BACKGROUND: The objective of this study was to identify psychiatric symptom patterns reported by individuals with phenylketonuria (PKU) in the outpatient clinic setting. METHODS: Brief Symptom Inventory (BSI) results, phenylalanine (phe) levels, and demographic information were collected through a retrospective chart review on 64 participants in the study, "A Diversified Approach for PKU Treatment" (ADAPT). RESULTS: The number of BSI scores meeting clinical threshold was significantly elevated for all global indexes and 6 out of 7 symptom subscales in patients with PKU. Recent and mean phe levels were correlated with age at the time of screening (R(2)=0.10, R(2)=0.10, respectively; p<0.05). Psychoticism and the Positive Symptom Distress Index (PSDI) scores were associated with metabolic control. CONCLUSIONS: The results of this study demonstrate a positive correlation between phe levels and psychiatric symptom severity in individuals with PKU.