Bipolar Disorders: Mixed States, Rapid-Cycling, and Atypical Forms

98 E. Vieta et al.Neurochemical studiesSiah et al. (1999) showed a trend towards higher platelet 5-hydroxytryptamine(5-HT) levels in bipolar I and II depressions when compared to normal controls,whereas there was no difference in platelet 5-HT levels between bipolar I and IIdepressed patients. The finding of increased platelet 5-HT levels in bipolardepressed patients compared to normal controls is consistent with the results ofprevious studies (Wirz-Justice and Puhringer, 1978; Stahl et al., 1983), and mightsuggest an increase in presynaptic 5-HT reuptake, presumably resulting fromdiminished synaptic 5-HT availability in this condition. When bipolar I and IIpatients were pooled, there was a trend toward a weak positive correlation betweenplatelet 5-HT and 21-item Hamilton Depression Rating Scale scores in the patientgroups, suggesting that the presumed deficiency of serotoninergic function mightbe related to the severity of depression. There were no differences in plasma3-methoxy-4-hydroxyphenylglycol (MHPG) levels between the three groups.Goodwin and Post (1975) had also found no difference in cerebrospinal fluidMHPG levels between bipolar I and bipolar II. In contrast, some studies suggestthat reduced urinary MHPG levels may be present only in bipolar I but not inbipolar II depressed patients (Muscettola et al., 1984; Schatzberg et al., 1989).Further studies are needed to explore the biochemical distinctions and similaritiesbetween bipolar I and bipolar II disorders.On the other hand, Emamghoreishi et al. (1997) showed that the baseline Ca 2+concentration was significantly higher in the B lymphoblasts from patients withbipolar I disorder, but not bipolar II disorder or major depression, than in healthysubjects or psychiatric patients with non-mood disorders. There were higher basalCa 2+ concentrations in T lymphocytes in male bipolar I patients, but not in menwith bipolar II patients or major depression, than in healthy male comparisonsubjects. Phytohemagglutinin-stimulated Ca 2+ concentrations did not differamong groups, but the percentage differences from basal Ca 2+ levels were lowerin bipolar I and depressed patients than in healthy subjects. The authors suggestedthat trait-dependent factors account, at least partly, for the higher basal lymphocyteCa 2+ concentration in bipolar I subjects.NeurophysiologyWith respect to sleep electroencephalography, no differences between bipolar Iand unipolar depressed patients have been reported by Giles et al.(1986), but theydid find differences between unipolar patients and bipolar II patients: bipolar IIpatients had longer rapid-eye-movement (REM) latencies, more non-REM time,and hypersomnia. Ansseau et al. (1984, 1985) found that depressed bipolar IIpatients had more variability in REM latency, as well as a trend toward more sleeponsetREM periods than bipolar I patients.