The diagnosis of psychiatric disorders in an individual with developmental disabilities (DDs) can be an extremely difficult challenge. Following several principles can simplify the diagnostic process.

Before the implementation of pharmacologic interventions, carefully assess the patient's overall psychosocial milieu. DD patients are extremely sensitive to their surroundings and have a limited behavioral repertoire of response. Thus, they may display their distress somatically.2 Even minor changes or fluctuations of a valued routine can present with problematic behavior. In addition, assessment also must involve the patients' family and any group or agency involved.

The level of disability often will determine the manifestations of psychiatric disorders. Several factors influence the evaluation of psychiatric symptoms in patients with DD:5

  • "intellectual distortion" limiting verbalization
  • poor social skills
  • cognitive deterioration exacerbating pre-existing deficits

Because much of a psychiatric evaluation is predicated on verbal reports of internal states, an evaluator may be extremely hampered and in unfamiliar territory. As a result, a process of "diagnostic overshadowing" may take place. Individuals with a DD and a coexistent mental disorder may be less likely to be labeled with a psychiatric diagnosis, even though they display the same manifestations as an individual without a cognitive impairment.3 In general, evaluators need to rely more on ancillary and collateral information about affected patients and to pay more attention to neurovegetative signs of mental illness.5

Adapted from: Barry JJ and Huynh N. Psychotropic drug use in patients with epilepsy and developmental disabilities. In: Devinsky O and Westbrook LE, eds. Epilepsy and Developmental Disabilities. Boston: Butterworth-Heinemann; 2001;205–217. With permission from Elsevier (

Authored By: 
John J. Barry MD
Nga Huynh PharmD
Reviewed By: 
Steven C. Schachter MD
Tuesday, June 1, 2004