BOSTON – Failure to use a developmental framework when assessing mental illness in children and adolescents with intellectual disabilities can hinder the accurate diagnosis of psychiatric disorders, and lead to inappropriate and possibly dangerous treatment, according to Lauren R. Charlot, Ph.D.

“It's important to consider the ways in which an individual's developmental stage affects his or her behavior and thoughts,” Dr. Charlot said at the annual meeting of the American Society for Adolescent Psychiatry.

“Some symptoms or behaviors that would seem pathologic for a typically developing individual may be 'typical' for a person with a particular set of skills and challenges, especially when under stress,” said Dr. Charlot, of the department of psychiatry at the University of Massachusetts, Worcester.

For example, she said, an adolescent with similar cognitive features to a typically developing preschool-age child might engage in self-talk–talking out loud to himself or herself–under stress. “Developmentally, this behavior is appropriate, but if you don't apply a developmental perspective, it seems abnormal and could easily be mistaken for psychotic ideation.”

The most important consideration when evaluating individuals with intellectual delays is the link between developmental stage and cognitive processes. Studies have identified multiple developmental effects on psychopathology in people with intellectual disabilities, Dr. Charlot noted. Among the developmental effects most likely to have an impact on psychiatric evaluation in this patient population are:

▸ Magical thinking, characterized by poor distinctions between fantasy and reality. “These kids may be talking to people who are not present, and they may be expressing wishes as beliefs,” Dr. Charlot said. Unfortunately, she added, “this behavior is often misconstrued as hallucinations or delusions,” even though it is a consequence of cognitive development rather than psychotic thinking.

▸ Prelogical thinking, which is characterized by primitive, incomplete thought processes and may present as seemingly tangential rambling. Normal among preschoolers, this mode of thought can be symptomatic of mental illness–particularly schizophrenia–in typically developing adolescents and adults, Dr. Charlot said. “This type of prelogical thinking is common at baseline in people with intellectual delays, and it tends to get exaggerated when they're under stress, which is often reported as 'racing thoughts.' But it's not a consequence of psychosis. It relates to an inability to understand logical relationships between subjects,” she said.

▸ Concrete thinking, whereby language and perceptions are interpreted literally. The limited ability to understand abstract language and ideas can lead individuals to misinterpret questions that are asked of them, which could be perceived as an indication of disturbed thought, Dr. Charlot said.

▸ Egocentrism, or the tendency to assume that everyone shares one's own thoughts and the inability to understand the consequences of one's own behavior on others. In normally developing children, egocentric behavior begins to wane after toddler and preschool stages. Therefore, when it presents in adolescents, it can be misconstrued as narcissistic or oppositional behavior, according to Dr. Charlot.

To avoid the “trap” of perceiving developmentally driven behaviors as symptomatic of mental illness in individuals with intellectual disabilities, “You need to ask the question: 'what is usual behavior for this patient?'” Dr. Charlot stressed. “Because the clinical population is highly heterogenous, you need to know what the individual person's baseline [behavior] is. You cannot use general population reference group [data] to determine that a symptom or symptoms are evidence of psychosis or other psychopathology.”

Additionally, Dr. Charlot continued, “ask yourself if the behaviors and symptoms are pathologic for a person functioning at this developmental level.” For example, if you are assessing an adolescent who appears labile and “all over the place,” she said, “that's not that unusual for an intellectually disabled individual who is experiencing stress.”

Before assuming that alterations in mood and behavior are indicative of a psychiatric disorder in adolescents with intellectual impairment, “hunt for possible sources of physical distress,” Dr. Charlot said.

Among the many medical problems that can manifest as behavioral issues are constipation, gastroesophageal reflux disease, seizure disorder, hypothyroidism, hypertension, anemia, candidiasis, urinary tract infection, diabetes, hypercholesterolemia, and obesity, she said, adding, “I can't tell you how many cases of adolescents with reported severe, aggressive behavior turned out to be constipated.”

Often, because of poor language skills, these individuals are unable to articulate physical complaints, resulting in agitation, which may then be attributed to a psychiatric disorder, she said at the meeting cosponsored by the University of Texas at Dallas.

Finally, if and when a psychiatric syndrome is identified, “be careful not to automatically attribute any future alterations in mental status or behavior as being secondary to the psychiatric problem,” Dr. Charlot said.

Under all circumstances, “comprehensive treatment should be directly derived from comprehensive assessment.”

Intellectual Impairment: Use Developmental Lens