Schizophrenics differ in their outcome mainly because different response and side effects to treatment, and clinicians do not have good instruments to choose the best antipsychotic (AP) for each individual. Weight gain is a frequently observed side effect with many AP treatments and seems to be underreported and under-recognized in many patients.

The potential effect of the Trp64Arg variant in beta3 adrenergic receptor gene on weight gain and obesity was investigated applying meta-analytic techniques, combining all published data while restricting our analysis to studies investigating the Trp64Arg in antipsychotic-induced weight gain and obesity. We also investigated whether ancestry (Caucasian versus African-American) and clinical factors moderated any association.

We found no evidence for association of the Arg64 allele with weight gain and obesity (z= 0.49 p = 0.626) but without significant between studies heterogeneity (chi-squared = 0.17 (d.f. = 1) p = 0.678).

Our meta-analysis does not provide support for the association of Trp64Arg in weight gain but indicates that firmly establishing the role of pharmacogenetics in clinical psychiatry requires much larger sample sizes that have been hitherto reported. On the other hand, the number of the studies employing psychotic patients is too small compared to the number of studies that have investigated this polymorphism in obesity.