Background: There is a substantial body of data showing differences in the functioning of the two hemispheres in unipolar depressive and bipolar disorders. Migraine is a frequent co-morbid disorder in these patients, and it has been proposed that migraine may be associated with left-handedness. It would therefore be interesting to study migraine and handedness in a population of patients with mood disorders.
Methods: A total of 201 patients with an index episode of either major depression or mania were interviewed with a semi-structured interview based partly on DSM-IV criteria and partly on TEMPS-I for affective temperaments. The criteria of the Headache Classification Committee of the International Headache Society were used to establish the diagnosis of migraine. Hand preference was assessed using the Edinburgh inventory, and the patients were classified as having right-, left-, or mixed-handedness.
Results: In the whole group 117 patients had migraine (58%) and 59 (29%) were classified as having non-right hand preference. There was a significant increased prevalence of non-right-handedness in the migraine group (37% vs. 19%, p=0.021, Chi-square test; OR 2.5; 95% CI 1.3 -4.8, p=0.007). In patients with cyclothymic, hyperthymic or irritable temperaments the prevalence of non-right-handedness (42%) was significantly higher (p=0.013, Chi-square test; OR 2.2, 95% CI 1.2-4.3) compared to patients with a depressive or no affective temperament (24%). The prevalence of non-right-handedness was also significantly higher both in patients with co-morbid eating disorders (48% vs. 26%, p=0.008 Chi-square test; OR 2.7, 95% CI 1.3-5.9, p=0.01) and asthma (45% vs. 26%, p=0.026 Chi-square test; OR 2.3, 95% CI 1.1-5.1, p=0.029).
Limitations: Non-blind evaluation of affective diagnosis, migraine and handedness.
Conclusions: Our main finding supports the hypothesis that non-right-handedness is associated with migraine and bipolar affective temperaments ("soft bipolarity") in a sample of patients with major affective disorders.