Blood trace element analyses fail to predict diagnosis.

The etiology of many developmental disabilities is unknown and, as a consequence, the diagnosis of disorders such as autism, learning disabilities, mental retardation, and emotional disturbances remains controversial. Traditionally, psychologists have relied on the use of psychometric data and clinical observations in order to arrive at a diagnosis and treatment plan for the developmentally disabled child. It is becoming apparent, however, that an array of biological and social factors may contribute to these nuances of human behavior, thus requiring a more sophisticated approach to diagnosis and treatment (Engel, 1977). One perspective that is currently being pursued is the interactive effects of nutritional and environmental factors on the behavior and learning ability of the disabled child. Indices of nutritional status, such as trace element profiles obtained from blood and hair, as well as indicators of exposure to environmental toxicants, such as lead and cadmium, have been examined in a descriptive manner involving learning-disabled (Pihl & Parkes, 1977; Massaro, Raiten, & Zuckerman, 1983), Down's syndrome (Barlow, Sylvester, & Dickerson, 1981), autistic (Shearer, Larson, Neuschwonder, & Gedney, 1982; Massaro et al., 1983), and mildly retarded children (Marlowe, Errera, & Jacobs, 1983), and interpretatively to predict academic achievement, cognitive functioning, and classification of childhood exceptionality and mental retardation (Pihl, Drake, & Varna, 1980; Pihl & Parkes, 1977; Massaro et al., 1983; Marlowe, Moon, Errera, & Stellern, 1983). A lack of consistent subject selection criteria and few attempts to replicate existing findings preclude one from arriving at any conclusions regarding the utility of trace element and heavy metal profiles as indicators of specific disorders and their applicability in a clinical setting.