Emotional health in early-treated adults with phenylketonuria (PKU): Relationship with cognitive abilities and blood phenylalanine

Introduction: Mental health, physical health, and cognitive skills have been scarcely investigated in the same sample of adults with PKU (AwPKU). This is striking since emotional difficulties may potentially contribute to cognitive impairments and vice-versa. Here we aim to fill this gap. 

Method: Thirty-six early-treated AwPKU and 40 controls were given an extensive battery of cognitive tasks assessing complex executive functions, inhibitory control, short-term memory, sustained attention, visuospatial attention, language production (reading and naming), visuomotor coordination, spoken language and orthographic processing. In addition, participants were given tasks taṆpping emotion recognition and completed questionnaires to assess depression (BDI-II), empathy (IRI) and mental/physical health-related quality of life (SF-36). 

Results: As a group, AwPKU performed significantly worse than controls especially in tasks tapping complex executive functions and across tasks when speed was measured but did not differ for emotional-health and physical health. In the PKU group, cognitive measures and measures of physical health-related quality of life were inter-correlated (differently than in the control group), and both measures were associated with metabolic control: better metabolic control, better cognition, and better physical health. Instead, cognitive measures and measures of emotional-health/mental-health-related quality of life did not correlate with one another and better metabolic control was not associated with better emotional health. Instead, some negative correlations were found. Better metabolic control was associated with worse perspective taking and more distress in socially stressful situations. Furthermore, difficulties in keeping the diet were associated with less emotional well-being. 

Conclusions: Taken together, these results indicate the advantages, but also possible emotional difficulties related to maintain a PKU diet, suggesting the importance of developing alternative therapy options.