Psychiatric Disorders in Adult Patients with Early-treated Phenylketonuria

Objective: To determine psychiatric disorders in patients with phenylketonuria (PKU) and to test whether biochemical control, intellectual functioning, white matter abnormalities visible on magnetic resonance imaging (MRI), and/or style of parenting influence psychopathology.

Design And Subjects: This cross-sectional study consisted of 35 PKU patients 17 to 33 years of age (mean: 22.2). From a total of 67 patients, 3 patients were selected because of other causes of possible brain damage. Then 35 patients were randomly drawn with comparison with a control sample (n = 181) from an epidemiologic study.

Methods: We used a standardized, highly structured, face-to-face interview; intelligence quotient (IQ) test; cranial MRI (n = 26); and monitoring of plasma phenylalanine.

Results: The overall rate of psychiatric disorders was 25.7% in PKU patients and 16.1% in controls. This difference was not statistically significant. The pattern of psychiatric disturbances was different for PKU patients and controls (Fisher's exact test): in PKU patients, externalizing disorders were reduced (PKU: not present, controls: 7.8%), whereas internalizing disorders (PKU: 25.7%, controls: 8.3%) were increased. International Classification of Diseases, version 10, diagnoses were predominantly those of the depressive category and more frequent in women (8 of 18 females and 1 of 17 males). A correlation between IQ and both biochemical control up to 12 years of age and school education of parents was confirmed. No correlation was found between the severity or pattern of psychiatric disturbances and school education of parents, biochemical control, IQ, or the extension of MRI-visible, white matter abnormalities. It was found that a restrictive controlling style of parenting is a risk factor for the development of psychiatric symptoms.

Conclusions: Our results support a psychological perspective for the development of psychiatric symptoms in PKU. Thus, optimizing medical treatment necessary to prevent brain damage should be accompanied by psychiatric monitoring and psychological support for the families.