Objectives. The aim of this study was to assess a relation between Val/Met COMT polymorphism and bipolar affective illness in a group of lithium-treated patients and also an analysis of this polymorphism in these patients, in relation to lithium prophylaxis effects.
Methods. The study was performed on 101 patients with bipolar affective illness (41 male, 60 female) treated with lithium for at least 5 years (5-20 years). The patients were divided into three groups in respect to their response to prophylactic lithium administration (ER – excellent responders, PR – partial responders, NR – lithium non responders). The control group consisted of 437 healthy persons (166 male, 271 female). All patients and healthy subjects were genotyped for Val/Met COMT polymorphism using PCR method.
Results. The distribution of genotypes Met/Met, Val/Met, and Val/Val of COMT polymorphism was significantly different in bipolar patients treated lithium compared with control group. In bipolar illness group, significantly higher percentage of Met/Met homozygotes and significantly lower percentage of Val/Met heterozygotes appeared. Genotype distribution was not accordant to Hardy-Weinberg principle. In lithium-treated patients a presence of Met/Met genotype was the most frequent in the group of NR patients (44%) and the least frequent in ER group (29%).
Conlusions. The results obtained show a difference of genotype distribution between lithium-treated bipolar patients and healthy control subjects. The preponderance of Met/Met homozygotes in bipolar patients may suggest an association of bipolar affective illness with a tendency to higher dopaminergic activity in prefrontal cortex. A finding of the study was also an association between Met/Met genotype and poorer response to prophylactic lithium treatment.