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Autism Spectrum Disorders: Identification and Implications of Associated Medical Conditions 

Autism Spectrum Disorders: Identification and Implications of Associated Medical Conditions

Autism Spectrum Disorders: Identification and Implications of Associated Medical Conditions

Margaret L. Bauman

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Points of Interest

  • Children, adolescents, and adults with ASDs, who experience common medical conditions, may not present with the same signs and symptoms as that exhibited by their neurotypical peers.

  • Many nonverbal, sensory disordered persons with ASDs may not be able to express or demonstrate their discomfort or localize pain.

  • Many of the medical conditions occurring in individuals with ASDs are treatable.

  • Treating medical conditions can improve physical comfort and quality of life and allow the individual to better participate in and benefit from services and interventions.

  • Some medical conditions may have genetic implications and may therefore aide in our ability to subtype groups of individuals on the autism spectrum.


The autism spectrum disorders (ASDs) are identified by behaviorally defined clinical features characterized by core symptoms of impaired social interaction, delayed and disordered communication/language, and isolated areas of interest. It is now recognized that individuals affected with ASDs are heterogeneous in terms of the cause of their disorder and the degree to which each is affected functionally and neurobiologically. Since its initial description in 1943 (Kanner), a growing body of research has broadened our perspective of the disorder and has created an environment whereby early diagnosis and intervention has become the standard of care, with the realization that in many cases, early identification and intensive therapies can lead to more positive developmental outcomes. With advancements in clinical care has come the observation and appreciation of the fact that many children with ASDs, adolescents and adults have medically relevant health-care issues that may go undetected because of atypical symptom presentation, the inability of the patient to describe or localize discomfort, and often behavioral issues that can make physical examination challenging. However, many of these medical conditions are treatable and, when identified and treated, may improve quality of life for the patient and his/her family and may broaden our understanding of the phenotypic expression of ASDs, leading ultimately to a better defined genotypic subtyping of individuals on the spectrum.


Autism is now considered one of the most common disorders of development worldwide. Studies performed by the United States Centers for Disease Control (CDC) in selected communities in 2002 suggest that the current prevalence rates for ASDs are approximately 1 in 150 children (Kuehn, 2007). The increase in the reported prevalence of ASDs has been attributed by some to improved ascertainment, a broadening of the diagnostic definition, and improved public and professional awareness. Others have attributed this upsurge in diagnosis to the contribution of potential, as yet to be identified, environmental factors.

Numerous epidemiologic studies have provided compelling evidence for a genetic basis for autism (Bailey et al., 1995; Bolton et al., 1994). Beginning with the seminal twin study of Folstein and Rutter, published in 1977, the concept of ASDs as a largely genetic disorder has remained in the forefront of autism research. In this study, the authors identified a higher concordance in monozygotic twins than in dizygotic twins. Since that time, numerous linkage studies have been reported, with the most frequently replicated findings being associated with chromosomes 7q, 15q, 22q, and 2q (Schaefer & Mendelsohn, 2008). Additional candidate genes of promise include γ-amino butyric acid (GABA) and serotonin transporter genes, engrailed 2, neuroligin, MECP2, WNT2, PTEN, and MET (Campbell et al., 2006, 2007). Many new loci and genes have been identified, and the reader is referred to the chapters related to genetics in this book for detailed data. Autism is four times more common in males than in females, with a higher ratio in milder forms of the disorder. Further, ASDs are associated with a significant familial recurrence, much higher than that seen in the general population. The reported recurrence risk has been estimated to be approximately 15% in families having one affected child (Landa et al., 2006, 2008; Lauritsen et al., 2005). If the family has two affected children, the recurrence rate for subsequent children increases substantially, up to 25% to 50% (Cook, 2001; Spence, 2004).

Despite modern technology and advanced research, only approximately 6% to 15% of individuals with autism will be found to have an identifiable genetic diagnosis. In addition, a number of syndromes have been associated with ASDs, including Fragile X Syndrome (FXS), tuberous sclerosis, Smith-Lemli-Opitz Syndrome, and Rett Syndrome (MECP2 mutations) (Schaefer et al., 2008; Geschwind, this book). Numerous genes have been investigated as possible candidate genes, but replicated findings are lacking. Current epidemiological studies of ASDs strongly suggest multifactorial inhertitance, including genetic heterogeneity with multiple major gene effects, possible contributing environmental effects, and physiologically linked processes with multiple genes.

One of the many additional potentially important risk factors for ASDs that has gained increased interest is the role of advanced parental age. In a recent study, Durkin et al. (2008) noted that in a study of 1251 children with complete parental age information and who were defined as having ASDs based on DSM-IV criteria, both maternal and paternal age were independently associated with autism. The authors also noted that firstborn offspring of two older parents were three times more likely to develop autism than were later born offspring. A number of potential mechanisms for these effects have been suggested, including age-related chromosomal changes, complications of pregnancy, or possible environmental exposures during pregnancy that could have mutagenic effects. In addition, given the apparent importance of birth order, the authors speculate that these children may be more susceptible to autoimmune responses affecting neurodevelopment or may be affected secondary to maternal exposure to neurotoxic chemicals, passed to the offspring transplacentally or in breast milk, in combination with advanced maternal age. Whatever the mechanisms involved, these observations warrant further investigation in a larger population of children with ASDs.

Clinical Presentation

Although it is now recognized that autism is a clinically and biologically heterogeneous disorder, those affected share a triad of common features that include atypical social interaction, delayed and disordered language, and a markedly restricted repertoire of activities and interests (American Psychiatric Association, 1994). Symptoms can range from relatively subtle and mild to very severe. For example, there may be a qualitative impairment in reciprocal social interaction as opposed to an absolute absence of social interaction. Social behaviors can range from a seemingly total lack of awareness of others to inappropriate eye contact and atypical social responsiveness. Communication skills can span from a total lack of verbal speech and intentional use of gesture to the presence of speech that is associated with atypical intonation, prosody, syntax, and grammar. Although the normal development of single-word receptive and expressive vocabulary may be present, pragmatic language may be significantly impaired. Many affected individuals demonstrate poor eye contact, echolalia, pronoun reversals, stereotypic and repetitive behaviors, sensory processing dysfunction, difficulty dealing with novelty, an obsessive reliance on routine, and some level of cognitive impairment. In very young children, the lack of a pointing response and joint attention and limited pretend play are frequent characteristics as early as age 12 months. Many affected individuals have exceptional islands of rote memory and outstanding isolated talents in the face of otherwise general functional disabilities (Rapin & Katzman, 1998). Although it was initially believed that approximately 75% of those affected with autism functioned in the mentally retarded range, more recent studies have found that fewer than half of affected individuals have significant cognitive impairment (Newschaffer et al., 2007).

Typically, those individuals with nonsyndromic or “essential” autism demonstrate few, if any, dysmorphic features and are generally described as very attractive appearing children. For many years, these children were believed to demonstrate no abnormalities of motor function, or if present, these deficits were believed to be merely associated symptoms. It has now become apparent that gross and fine motor dysfunction is more common than previously appreciated. Numerous clinical studies indicate that children with autism exhibit deficits in skilled motor performance in response to command and with tool use, suggestive of a more generalized dyspraxia (Rogers et al., 1996; Mostofsky et al., 2006). Children with autism often show delays in learning novel complex motor skills such as peddling a tricycle or pumping on a swing with their legs (Gidley Larson & Mostofsky, 2007). Further, in a study of motor impairment in a group of 154 children with ASDs, Ming et al. (2007) noted that hypotonia was the most common motor symptom in this cohort, with motor dyspraxia being more prevalent in younger children than older children. Gross motor delay was reported in 9% and toe-walking in 19%. The etiology of motor dysfunction in ASDs remains uncertain, with abnormalities of the cerebellum, basal ganglia, and/or neural connections across distributed networks being hypothesized (Gidley Larson et al., 2008).

Examination of the autistic child, adolescent, and adult may be complicated by variable levels of cooperation, impaired communication and behavioral issues. Important factors during the physical and neurological assessments should include identification of potential dysmorphic features that might suggest a specific diagnosis or syndrome. Measurements of head circumference throughout childhood has resulted in the observation that a subset of children with ASDs demonstrate a larger than average head circumference, with approximately 20% of these showing a frank macrocephaly of greater than 98% for age and sex. More recent work by Lainhart et al. (2006) highlights the fact that the distribution curve of head size in ASD is similar to that seen in typically developing children but is shifted to the left, suggesting that this unusual head growth may reflect an upregulation of as yet unknown growth factors. The clinical finding of macrocrania is, at this time, without a defined neuropathological correlate.

All patients with autism should have a formal audiogram. Many children with ASDs present with impaired receptive and expressive language and fail to respond to the spoken word, causing some parents to wonder if their child might be deaf. Impaired hearing could alter communication and socialization skills. There is a debate as to the role of electroencephalography (EEG) as part of the routine evaluation of a child with an ASD. Although there are reports of autistic-like symptoms in some children with seizure disorders and an acquired aphasia (Landau Kleffner Syndrome), this disorder is very rare. In general, EEG is probably not indicated as a routine part of the ASD evaluation unless there is a clinical history to suggest a possible seizure disorder. Similarly, cranial imaging studies are not routinely recommended unless abnormalities on neurological examination are observed (Filipek et al., 1999). Additional assessments should include high-resolution karyotype and Fragile X Syndrome studies as an initial step, along with assessments from a speech and language pathologist, an occupational therapist, and a cognitive developmental specialist.

Associated Medical Disorders

Until recently, much of the clinical and basic science research has been focused on the understanding of brain mechanisms that could explain the behavioral, cognitive, social interaction, and communication dysfunction associated with ASDs, with relatively little attention to the possible significance of accompanying medical conditions. Much of this relative neglect may be related to the fact that the physical examination of an individual with autism, particularly children, can be challenging and often limited by poor patient cooperation and difficult office behavior. Further, it now appears that ASD individuals, many of whom are nonverbal or hypo-verbal, may not be able to describe or localize their discomfort. In addition, there is a growing appreciation that persons with ASDs may not present with typical, easily recognized symptoms, making diagnosis in any one circumstance difficult, and therefore overlooked. Research indicates that children with ASDs are more likely than other children with special needs to have difficulty accessing medical care, further compounding the challenge of providing quality routine health care to this population of individuals (Kogan et al., 2008). The fact that a child has autism does not rule out the possibility that he or she may have one or more other illnesses or disorders, similar to those experienced by typically developing children. Identifying and treating these disorders may improve behavior, developmental progress, and quality of life as well as provide leads into potential subsets of individuals with ASD who may have genetic and etiologic implications.

Pain and Discomfort

It is known from the general pediatric literature that typically developing children often show increased rates of problem behaviors in association with physical illness. For example, increased rates of head-banging behavior has been reported in infants who are experiencing middle ear infections (Lissovoy, 1962), and increased frequency of temper tantrums has been observed in toddlers in relationship to upper respiratory infections (Hart et al., 1984). Not surprisingly, physical illness is common in persons with developmental disabilities, and at least one study has suggested that the number of associated medical conditions may be higher for individuals with developmental disabilities than for the general population across the life span (Cooper, 1998). As is the case for typically developing persons, there also appears to be an association between physical illness and problem behaviors in the disabled population. Problem behaviors have been associated with illnesses such as allergies (Taylor et al., 1993), constipation (Lekkas & Lentino, 1978), premenstrual syndrome (Kennedy & Meyer, 1996), and urinary tract and ear infections (Gunsett et al., 1989). Documentation that problem behaviors may be causally linked to physical illness has been provided through studies showing that these behaviors can be significantly reduced as the result of appropriate medical diagnosis and treatment (Ghaziuddin et al., 1993; Peine et al., 1999). It has been suggested that this relationship between physical illness and problem behaviors is not the result of the illness itself but is more likely related to the degree of pain and discomfort experienced by the individual at any given time (Horner et al., 1996; Kennedy & Thompson, 2000).

Determining the causes and source of pain and discomfort can be challenging in nonverbal persons who may not process or localize sensory information accurately. Further, many persons with developmental disabilities, including individuals with ASDs, may not present with the typical signs and symptoms of illness familiar to most primary care physicians and specialists. For example, some ASD persons suffering from gastrointestinal disorders may present with aggression and self-injurious behavior without evidence of vomiting, diarrhea, constipation, or signs of abdominal discomfort (Buie, clinical observation). Thus, a high index of suspicion for some type of medical illness should be raised for any ASD or developmentally disabled patient who presents with an unusual onset or escalation of problem behaviors that have not responded to behavioral and environmental accommodations and that cannot be readily explained. Carr and Owen-DeSchryver (2007) have suggested the use of retrospective and prospective questionnaires, administered by knowledgable informants, to assist in delineating a potential connection between problem behavior and physical illness. In a study of 11 individuals with ASDs, ages 4 to 21 years, the authors noted that retrospective questionnaires alone were often unreliable. The addition of a prospective questionnaire allowed informants to track the association between behaviors and illness-related pain over a period of months and on a daily basis. Informants were supplied with a list of motor and verbal pain indicators derived from the pediatric clinical literature. The resulting data proved reliable in that informants were able to agree among themselves with regard to their observations. Of further concern is the observation that without prevention and prompt intervention, problem behaviors may become more strongly established over time (Horner et al., 2002).

Space does not allow for a detailed description of the multiplicity of possible medical conditions that may affect a person with autism. Therefore, only some of the more common disorders will be briefly highlighted here. These include seizure disorders, sleep disturbances, gastrointestinal disorders, metabolic dysfunction, and hormonal imbalances. However, the primary care and specialty physicians serving persons with ASDs must be constantly alert to a wide range of medical possibilities at any one time.

Seizure Disorders

The prevalence of seizures in adults with autism has been estimated to be between 20% and 35% (Minshew et al., 1997; Tuchman, this book), and in children with ASDs, it has been estimated between 7% and 14% (Rapin, 1996; Tuchman et al., l991), with peak risk periods occurring in early childhood and adolescence (Volkmar & Nelson, 1990). Although regression of language and cognitive skills in association with seizures has been reported during the teenage years, little is known regarding its etiology or prevalence (Minshew et al., 1997). Seizures may be of any typ,e but partial complex seizures are most frequently reported. The clinical identification of partial complex seizures in autistic individuals can often be complicated by the presence of atypical behavioral patterns and body movements often seen in association with ASDs and frequently attributed to the autism per se. Alternatively, not all body movements or mannerisms observed in ASDs are seizure-related and may be manifestations of other medical conditions such as gastroesophageal reflux disease (GERD) (Buie, 2005). Further complicating diagnosis is the fact that there may be a lack of direct correlation between clinical seizures and EEG activity (Minshew et al., l997). However, any behaviors such as staring, cessation of activity, eye fluttering or aggressive behavior associated with confusion should raise the suspicion of a complex partial seizure and further evaluation pursued. Obtaining a high-quality EEG—especially in toddlers and young children—can be difficult but can be achievable. Prolonged or overnight EEG can often be helpful as well as the use of video tape review of the events recorded in the home or school. A growing number of anticonvulsant medications are now available, and these seizures can usually be brought under control with experienced medical management.

Gastrointestinal Disorders

Although gastrointestinal (GI) dysfunction is believed to be relatively common in autism, the true prevalence of these disorders is unknown (Buie, 2005; Campbell et al., 2009). Similarly, it is not known whether these disorders are more common in persons with ASDs than in typically developing individuals. However, a recent, well-controlled prospective study, using a structured interview, reported a significantly increased prevalence of GI conditions in ASDs as compared to controls (Valicenti-McDermott et al., 2006). Parents often report a number of symptoms in their babies and young children, including diarrhea, constipation, food intolerance, gas, bloating, abdominal pain/discomfort, and a history of reflux (Horvath et al., 1999; Quigley & Hurley, 2000).

Although many children with ASDs present with typical GI track symptoms, others may not and may instead exhibit aggressions and self-injurious behavior, facial grimacing, chest tapping, and the seeking of abdominal pressure (Buie, personal communication). It is well-known that typically developing children can and often do present with behavioral disruptions when not feeling well. There is no reason to believe that children with ASDs should do otherwise. The identification of GERD, gastritis, esophagitis, colitis, inflammatory bowel disease, Crohn’s disease and celiac disease have been identified in autistic persons and treatment of these disorders have resulted in improved behavior and better developmental progress (Buie, personal communication), no doubt because the individual is more comfortable and physically well.

Recently, Campbell et al. (2009) have reported that disrupted MET gene signaling may contribute to increased risk for ASDs, including familial GI dysfunction. A functional variant in the promotor of the gene encoding the MET receptor tyrosine kinase has been associated with ASDs, and MET protein expression has been found to be decreased in the temporal lobe cortex in ASD postmortem brain tissue. MET is a pleiotropic receptor that is known to function in both brain development and GI repair. Thus, the identification of medical disorders in ASD individuals (in this case GI disorders) may not only improve quality of life for those affected with ASDs but may lead to improved or more precise definition of genetic and phenotypic subtypes in this complex heterogeneous disorder.

Sleep Disorders

The prevalence of sleep disorders in typically developing children is said to be approximately 30% and appears to be more common in early childhood (Ferber, 1996). In contrast, the prevalence rates among children with autism have been estimated to range from 44% to 83% (Richdale, 1999), and sleep disorders have been reported to be more severe in this population (Malow et al., 2006). It is known that disordered sleep affects daytime health, neurocognitive dysfunction, and behavioral disruptions in a variety of psychiatric and neurologic conditions. In typically developing children, sleep disruption may lead to daytime sleepiness and may manifest itself as hyperactivity, inattention, or aggression (Owens et al., 1998). Insomnia, defined as having trouble initiating and/or maintaining sleep, is the most common feature reported by parents of autistic children. Additional sleep concerns include symptoms of disordered breathing associated with loud snoring, noisy breathing, or occasional pauses or apneas in breathing as well as leg movements and tooth grinding. Occasionally, nocturnal arousals associated with screaming, walking, or confusion have been reported. These sleep disturbances may have multiple causes. Trouble initiating sleep may be related to hyperactivity or medications used to treat hyperactivity. Anxiety, depression, seizure disorders, or abnormalities of circadian rhythm have also been associated with delayed sleep onset.

Although disorders of arousal and behavioral noncompliance may also be factors, one must also consider other medically based disorders. It is known, for example, that GE reflux can contribute to nighttime awakenings in infants as well as older children (Buie, unpublished data). Loud snoring and daytime mouth breathing may suggest enlarged tonsils and/or adenoids as possible factors (Owens et al., 2000). Further, both obstructive and sleep apneas have also been reported in some cases. Given that there is increasing evidence that poor quality and quantity of sleep can have a negative effect on daytime behavior and functioning (Malow et al., 2006), it is important to accurately diagnose and treat reported sleep disruptions in individuals with ASDs.

Metabolic Disorders

Metabolic disorders are considered a rarity among patients with neurodevelopmental disorders, a reported diagnostic yield after initial evaluation varying from 1% to 2.5% (van Karnebeck et al., 2005). Although rare, the effect of correct diagnosis and treatment of a metabolic disorder may have a substantial effect on the patient’s developmental outcome. Engbers et al. (2008) performed repeated metabolic studies on a series of 433 subjects with neurodevelopmental disorders whose initial metabolic assessments were said to be normal and identified 12 metabolic diseases (2.8%), some of which were treatable. The prevalence of metabolic disorders in ASDs remains as yet largely unknown with the level of frequency no doubt varying with the specific disorder.

Smith-Lemli-Opitz Syndrome (SLOS) is one of the more common metabolic disorders associated with clinical features of autism (Bukelis et al., 2007). SLOS is an autosomal recessive disorder associated with an inborn error of cholesterol synthesis caused by mutations of the 7-dehydrocholesterol reductase gene (DHCR7) located on chromosome 11q12-13 (Kelley et al., 2001). Cholesterol is essential for neuroactive steroid production, growth of myelin membranes, and normal embryonic and fetal development. It is also believed to modulate oxytocin receptors, ligand activity, and G-protein coupling of the serotonin-1A receptor (Aneia & Tierney, 2008). It has been hypothesized that a deficit in cholesterol may disrupt these biological mechanisms, thereby contributing to clinical features of ASDs as observed in SLOS. The syndrome has an estimated incidence of 1 in 20,000 to 1 in 60,000 births and a carrier frequency of about 1%. Clinical characteristics include developmental delay, facial anomalies (ptosis, upturned nares, small chin, bitemporal narrowing, and microcephaly), and abnormal webbing between the second and third toes. Additional symptoms can include irritability, hyperactivity, self-injury, temper tantrums, and aggression. In mild cases, the physical features may not be readily recognizable. It has been estimated that approximately 50% to 75% of individuals with SLOS may meet criteria for autism. A clinical diagnosis of SLOS can be confirmed by means of biochemical analysis, an elevated level of plasma 7-dehydrocholesterol relative to the cholesterol level establishing the diagnosis. This disorder is not only identifiable but partially treatable with cholesterol supplementation, thus increasing the importance of syndrome recognition.

A number of studies and case reports have suggested that mitochondrial disorders may be a causative factor in a subset of autistic individuals. In 2005, Oliveira et al. published a population-based survey among school-aged children with ASDs and found that 7% of those who underwent a complete metabolic evaluation were diagnosed with a mitochondrial respiratory chain disorder. Further, this group reported that the affected children were clinically indistinguishable from children suffering from ASDs without a mitochondrial dysfunction. More recently, however, Weissman et al. (2008) reported their findings on 25 ASD subjects with biopsy-proven mitochondrial disorder and found that a series of “clinical red flags” could distinguish the affected children from those with idiopathic ASD. These “red flag” characteristics included the involvement of at least one non-neurological organ system, significant gross motor delays, easy fatigability, and repeated regressions after age 3 years. Further, they noted a nearly even distribution between males and females. The authors concluded that with careful clinical and biochemical assessments, children with the co-occurrence of ASDs and mitochondrial dysfunction could be distinguished from those with idiopathic ASDs and that those affected with mitochondrial disorders may represent a significant subset of individuals with autism.


Decreased bone mineralization and osteoporosis, once believed to be health issues found in the elderly, is now being recognized with increasing frequency in younger populations, including in childhood. This process is driven to a large extent by nutritional status, calcium, and vitamin D intake (Lehtonen-Veromaa, 2002; Foo et al., 2009; Davies et al, 2005). Thus, conditions associated with poor nutrition during childhood and adolescence, a critical period for bone mass accumulation, may significantly impact on the attainment of healthy peak bone mass. Gastrointestinal disorders appear to be prevalent among children with ASDs and may be more common in this population than among typically developing children (Valicenti-McDermott et al., 2006). Those with ASDs often demonstrate unusual eating patterns, frequently self-initiated, or may be placed on restrictive therapeutic or complementary alternative diets that limit the intake of calcium and vitamin D, the most common being the casein- and/or gluten-free diet. Additional factors may include impaired growth hormone secretion (Ragusa, 1993), low muscle tone (Ming, 2007), limited exercise (Pan, 2008), anticonvulsant medications (Chou et al, 2007; Pack et al., 2008), and the use of psychotropic or stimulant medications to control behaviors that may impact hormonal function, weight gain, and caloric intake (Bostwick et al., 2009; Ziere et al., 2008). Thus, although ASD individuals often have one or more of these well-documented risk factors, there are very few studies that have assessed the impact of any or all of these factors on bone density in ASD. A recent report of decreased cortical bone thickness in ASD children suggests that individuals with autism may be at high risk for the development of osteoporosis (Hediger et al., 2008). Given the potential risk of injury and fractures, as well as general health issues related to under-nutrition in this population, more research is needed.


New evidence suggests that children with chronic conditions may be predisposed to being overweight and to obesity. In a recent study, Chen et al. (2009) analyzed reported height, weight, and body mass index (BMI) from 46,707 subjects, ages 10 to 17 years, with the goal of measuring the prevalence of obesity adjusted for demographic and socioeconomic factors. Obesity was defined as 95% or more of the sex-specific BMI for age growth charts. The prevalence of obesity among those without a chronic condition was 12.2%. Among those subjects with chronic conditions, the prevalence of obesity was highest among children with autism (23.4%), followed by those with asthma (19.7%), learning disabilities (19.3%), attention deficit/hyperactivity disorder (18.9%), and hearing/vision conditions (18.4%). The rising rate of obesity in the general population has been attributed to greater nutritional accessibility and more sedentary lifestyles. Although the causes of obesity are recognized to be heterogeneous, environmental and genetic factors have become the focus of intensive research. Numerous national studies have suggested that exposure to television is associated with obesity, lipid disturbances, and poor cardiovascular health during adulthood (Gortmaker et al., 1996; Robinson, 1999). The explanation for this correlation is the concept that television promotes significant lifestyle changes related to an imbalance of caloric intake and expenditure (Coon & Tucker, 2002). Medications that many children, adolescents, and adults with ASDs receive to control seizures, such as valproic acid (Verrotti et al., 2002), or disruptive behavior, such as risperidone (Saddichha et al., 2007), have been associated with excessive weight gain in some cases and may therefore also be contributing factors.

Earlier studies have found similar statistics. For example, a sample of 140 Japanese children with ASDs, ages 7 to 18 years, revealed that 25% were classified as obese (Sugiyama, 1991). In a somewhat later study involving 20,031 children with mental retardation, ages 6 to 17 years, 413 of whom were children with autism, Takeuchi (1994) found the prevalence of obesity to be 22% in boys and 11% in girls. Curtin et al. (2005) more recently reported similar findings in which the overall prevalence for at-risk-for-overweight was 35.7%, and for overweight was 19% among children with ASD. When the data were stratified by age, the prevalence for at-risk-for-overweight and overweight appeared to be highest in the 12- to 17.9-year age group. These observations were echoed in a similar study of 380 boys and 49 girls with autistic disorder. However, the authors noted that at-risk-for-overweight/overweight in autistic children had no relationship to the core features of the disorder and that older age was a predictor of lower height and at-risk-for-overweight among these children (Xiong et al., 2005).

It is well-known that children with autism have different dietary patterns and lifestyles when compared to typically developing children. These factors can affect body growth and nutritional conditions. Although many reports have been directed toward the concern for obesity in ASDs, some studies have reported a tendency toward being underweight among children with autism and Asperger’s Syndrome, often associated with delayed physical growth, and generally attributed to low appetite, narrow range of food choices, and digestive disorders (Bolte et al., 2002; Hebebrand et al., 1997; Lesinskiene et al., 2002). Thus, there is significant concern regarding diet, nutrition, physical activity, and therapeutic interventions, which—either separately or in combination—may contribute to serious health-related issues such as diabetes, hypertension, hyperlipidemia, anemia, and osteopenia, to name a few. The role played by potential genetic and environmental factors interacting with dietary and therapeutic approaches will be important topics for future research.

Hearing Impairment Many children with autism present initially with delays in expressive and receptive language and it is not unusual for a parent to comment that they wondered whether their child might be deaf. Thus, the assessment of auditory abilities in children with ASDs is important in the diagnosis and treatment of this disorder. A small number of studies have investigated the prevalence of hearing impairment within the ASD population. In a study of 199 children with ASDs and adolescents who were audiologically evaluated, mild-to-moderate hearing loss was identified in 7.9% and unilateral hearing loss in 1.6% (Rosenhall et al., 1999). In this same study, profound bilateral hearing loss or deafness was found in 3.5% of all cases. These findings represent a prevalence significantly higher than that observed in the general population and was comparable to that found among individuals with mental retardation. Further, hearing deficits among the ASD subjects occurred at similar rates, regardless of intellectual functioning. Of additional note is the fact that hyperacusis was found in 18.3% of the autism group as compared to 0% in the non-autism comparison group. Similarly, the rate of serous otitis media was found in 23.5% of ASD subjects with a related conductive hearing loss noted in 18.3%, both of which appeared to be increased in persons with autism. Similar concerns have been raised by the more recent study of Tas et al., (2007), raising the suspicion that hearing loss may be more common in children with autism than in typically developing children.

Gynecological Dysfunction in Adolescence

One of the many medical conditions that has not yet been well-studied relates to the potential effects of hormonal imbalance, especially during adolescence, which could be associated with precocious puberty, accelerated or reduced physical growth, and/or behavioral disruptions associated with menstrual pain or discomfort. These factors have been raised in a study published by Carr et al. in 2003, in which both physical discomfort and pain associated with the menstrual cycle were cited as possible causes of problem behaviors in adolescence. The authors, however, also raised the possibility that fluctuations in progesterone and estrogen levels might also be an important variable. This theme has been further expanded in a more recent study in which adolescent girls with autism, Down syndrome, and cerebral palsy were evaluated retrospectively regarding gynecological complaints. Girls with autism were significantly more likely to present with behavioral issues than the other two groups. Management included the use of non-steroidal anti-inflammatory drugs, oral contraceptives, and education (Burke et al., 2009). Further studies are needed in this important area to provide correct diagnoses and appropriate interventions.


Routine medical conditions frequently seen in typically developing individuals, as well as their behavioral implications, have yet to be fully investigated in children, adolescents, and adults with autism (Gilberg, this volume). The frequency and presence of recurrent ear infections, sinusitis, asthma, hypertrophied tonsils and adenoids, urinary tract infections, spastic bladder that be associated with new onset incontinence at any age, attention deficit disorder, disordered sensory processing, allergies, or any other medical condition commonly seen have yet to be carefully considered in autism. These conditions may not always present with the typical signs and symptoms that most physicians have been taught to recognize but should be considered in ASD individuals at any age who present with unexplained and/or changes in behavior. Defining and treating these medical conditions can improve quality of life for the patient as well as his or her family and can be associated with improved developmental gains as the result of better physical health. Further, there is a growing sense that at least in a subset of affected individuals, ASD may involve multiple organ systems. Thus, understanding the biological mechanisms associated with these other organ systems, in addition to expanding our knowledge about the brain in persons with autism, could potentially expand our knowledge and provide insights into the underlying neurobiology of the disorder.

Much progress has been made in the identification and treatment of persons with ASDs, as well as our understanding of the etiologic and biological mechanisms that are or can be associated with the disorder. However, much remains to be unraveled and many questions remain unanswered. With advancing technology and improved medical and diagnostic assessments of those affected with ASDs and their families, it is hoped that diagnoses can be made earlier—potentially at or before birth— and that more effective therapies and interventions will become possible to improve the lives of those affected with autism.

Challenges and Future Directions

  • Children, adolescents, and adults with ASDs may not present with the typical signs and symptoms easily recognized by most health-care professionals.

  • ASD individuals who present with challenging behaviors such as aggression and self-injury, especially if they are nonverbal, should be evaluated for an underlying medical condition, before assuming that these disruptions are “just behavioral” or “just part of the autism.”

  • Health-care professionals and caregivers need to learn the signs and symptoms of pain and discomfort in nonverbal or hypo-verbal, sensory-impaired persons with ASDs.

  • Some comorbid medical conditions may have genetic and biologic implications that may provide insight into some of the underlying mechanisms related to etiology and phenotypic expression of ASDs and could potentially aide in defining some treatment modalities in the future.

Suggested Readings:

Buie, T., Campbell, D. B., Fuchs, G. J., et al. (2010). Evaluation, diagnosis and treatment of gastrointestinal disorders in individuals with ASDs: A consensus report. Pediatrics (Suppl), 125, S1–S18.Find this resource:

Coury, D. (2010). Medical treatment of autism spectrum disorders. Current Opinion in Neurology, 23, 131–136.Find this resource:

Oliveira, G., Diogo, L., Grazina, M., et al. (2005). Mitochondrial dysfunction in autism spectrum disorders: A population study. Developmental Medicine and Child Neurology, 47, 185–189.Find this resource:


American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.; DSM-IV). Washington, DC: APA.Find this resource:

    Aneia, A., & Tierney, E. (2008). Autism: The role of cholesterol in treatment. International Review of Psychiatry, 20, 165–170.Find this resource:

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