Mild learning difficulties and offending behaviour--is there a link with monoamine oxidase A deficiency?
Level 4 - case-series / case-control
Case series / cross-sectional screening study in a selected clinical cohort without a control group.
PubMed 11702062 · doi:10.1097/00041444-200109000-00012
What was done
Researchers attempted to replicate findings linking monoamine oxidase A (MAO-A) deficiency to borderline intelligence and aggressive or antisocial behavior. They identified 54 male patients with matching clinical characteristics in secure mental health facilities in England and Wales. Participants were evaluated using the antisocial personality disorder section of the SCID-II interview, medical chart review for offending history and family background, and blood and early-morning urine sampling to analyze biogenic amine metabolite ratios (normetanefrine to vanillylmandelic acid).
What was found
Urinary metabolite screening initially identified two potential cases of MAO-A deficiency, but both tested negative upon resampling, resulting in zero confirmed cases among the 54 participants. No additional numerical data or sequencing results were reported in the abstract.
Why it matters
These findings suggest that overt MAO-A deficiency is an uncommon cause of mild intellectual impairment combined with severe offending or antisocial behavior in secure psychiatric settings.
Limits
The study had a small sample size (n = 54) confined exclusively to institutionalized male patients in England and Wales. The screening relied on urinary metabolite ratios rather than comprehensive direct sequencing across all participants, and no healthy or non-offending control group was included.
Cited by
- contradicts A subsequent study identified rare MAOA mutations in several other impulsively aggressive boys referred to a hospital.