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The dopamine hypothesis of schizophrenia and the emphasis on other neurotransmitters, most notably norepinephrine, serotonin, and acetylcholine, in the pathogenesis of depression, have focused attention away from substantial evidence implicating dopamine in affective disorders. The clinical evidence includes alterations in depressive symptoms with aging (concomitant with possible changes in dopamine metabolism), potential dopaminergic involvement in several subtypes of depression, similarities between some of the symptoms of Parkinson's disease and those of depression (including psychomotor retardation and diminished motivation), and potential dopaminergic abnormalities in seasonal mood disorder. The biochemical evidence in patients with depression derives from studies of homovanillic acid, a dopamine metabolite, indicating diminished dopamine turnover. In addition, there is a considerable amount of pharmacologic evidence regarding the efficacy of antidepressants with dopaminergic effects in the treatment of depression. We conclude that dopamine likely contributes significantly to the pathophysiology of depression. However, the role of dopamine in this syndrome must be understood in the context of existing theories involving other neurotransmitters which may act independently, and interact with dopamine and other neurochemicals, to contribute to depression.

Binding characteristics of tritiated imipramine were determined in the frontal cortex of suicides and well-matched controls. Maximal binding was significantly lower in brains from the suicides. This finding is consistent with reports of decreased tritiated imipramine binding in the platelets of patients diagnosed as having a major affective disorder.

Positive symptoms of schizophrenia were diminished by neuroleptics and increased by amphetamine and accounted for most of the change seen in the total Brief Psychiatric Rating Scale (BPRS). Negative symptoms in the same subjects were not affected by neuroleptics but increased after amphetamines to a degree that just attained statistical significance. This increase was due to one item (emotional withdrawal) of the negative symptom factor which responded to neuroleptics and amphetamines as did positive symptoms. These findings are discussed with respect to new ideas about the role of dopamine in schizophrenia.

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For over half a century, lithium has been the gold standard amongst the pharmacological armamentarium used to treat bipolar disorder. Its ascendancy in this regard has been attributed partly to its primacy of discovery and clinical implementation; however, it is important to consider how it has achieved success and retained its prominence and whether this is because of its unique profile and specificity of actions. In this paper, we briefly discuss the clinical evidence in support of lithium specificity and argue for its continuing use in those patients most likely to benefit, namely, patients with 'classic' bipolar disorder. Further, we suggest that accurate characterization of 'lithium responders' through focused research is likely to yield novel treatments and assist in better understanding of the pathophysiology of the illness. In addition, the unique antisuicidal actions of lithium warrant further examination, as do its impressive properties as a prophylactic agent. This is particularly so given the high morbidity associated with bipolar disorder and its potential for suicide. Hence, in this paper, after describing the changing diagnostic backdrop against which much of the research to date has been conducted, we discuss the clinical therapeutic profile of lithium in both the acute and long-term management of bipolar disorder and its phenotypic specificity of action. We demonstrate that lithium possesses significant clinical and therapeutic efficacy that is very individual and thus remains the treatment of choice for bipolar disorder when used specifically in select patients.

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