Seasonal depression: the dual vulnerability hypothesis revisited.

OBJECTIVE: In DSM-IV, winter seasonal affective disorder (SAD) is classified as a seasonal pattern of recurrent major depressive episodes in winter with full remission of symptoms in summer. However, other groups with "winter depression" have been identified, including patients with incomplete summer remission (ISR) and subsyndromal SAD (sub-SAD, winter depressive symptoms that do not meet criteria for major depression). In this study, we compare the clinical characteristics of these three seasonal groups and their response to light therapy. METHOD: 558 patients assessed at a specialized SAD Clinic were diagnosed using DSM-III-R or DSM-IV criteria. Clinical information was recorded using a checklist at index assessment. A subset of patients (N=192) were treated with an open, 2 week trial of light therapy using a 10000 lux fluorescent light box for 30 min per day in the early morning. Patients were assessed before and after treatment with the 29 item modified Hamilton Depression Rating Scale and clinical response was defined as greater than 50% improvement in scores. RESULTS: The rates of some melancholic symptoms, anxiety, panic, suicidal ideation, and family history of mood disorder were lowest in the sub-SAD group. The clinical response rates to light therapy were highest in the sub-SAD group (N=32, 78%), intermediate in the SAD group (N=113, 66%), and lowest in the ISR group (N=47, 51%). LIMITATIONS: This was a retrospective study of patients seen in a specialty clinic, although information was obtained in a standardized format. The light therapy trial had an open design so that placebo response could not be determined. CONCLUSIONS: There are differences in both the patterns of clinical symptoms and the response to light therapy in these three groups with winter depression. These results are consistent with a dual vulnerability hypothesis that considers these groups to result from interaction of separate factors for seasonality and depression.

Effects of light therapy on suicidal ideation in patients with winter depression.

BACKGROUND: Recent case reports suggest that some patients with seasonal affective disorder (SAD) may become suicidal after initial treatment with light therapy. This retrospective study sought to determine the effects of light therapy on suicidal ideation in patients with SAD. METHOD: The cases of 191 depressed patients with SAD by DSM-III-R or DSM-IV criteria treated with an open trial of morning light therapy using cool white fluorescent light boxes (2500 lux for 2 hours per day or 10,000 lux for 30 minutes per day) for 2 weeks were retrospectively analyzed. Patients had been rated before and after treatment with the expanded Hamilton Depression Rating Scale (SIGH-SAD). RESULTS: Sixty-seven percent of patients were rated as clinical responders to light therapy. There was significant improvement in the SIGH-SAD suicide item score, with 45% of patients showing a reduction in score. Only 6 patients (3%) had slight worsening of suicide scores. No patients attempted suicide or discontinued light therapy because of emergent suicidality. CONCLUSION: Light therapy relieves suicidal ideation in patients with SAD consistent with overall clinical improvement. Emergence of suicidal ideas or behaviors is very uncommon with light therapy.

Effects of rapid tryptophan depletion in patients with seasonal affective disorder in natural summer remission.

BACKGROUND: Serotonergic mechanisms have been proposed for the pathophysiology of seasonal affective disorder (SAD) and the therapeutic effect of bright-light treatment. Previously, we showed that SAD patients, in clinical remission with light therapy during the winter, experienced transient depressive relapses after a rapid tryptophan depletion (RTD) technique, which results in decreased brain serotonin levels. The objective of this study was to investigate the effect of RTD in SAD patients who were in natural summer remission. METHODS: Twelve drug-free patients with SAD by DSM-IV criteria and 10 normal subjects participated in this double-blind, placebo-controlled, crossover study. SAD patients were in natural summer remission for at least 8 weeks. Behavioural ratings and plasma tryptophan levels were obtained before, and 5 h after, ingesting an amino acid (AA) mixture +/- tryptophan. Experimental RTD and control sessions were scheduled 1 week apart. RESULTS: The RTD session resulted in significant reduction in total and free plasma tryptophan levels compared to the control session. The behavioural data were analysed using repeated measures analysis of variance. This analysis found significant main effects of time (higher scores after AA ingestion) and diagnosis (higher scores in SAD patients), but no main effect of session or significant interaction effects between the three factors. Thus, there were no significant behavioural effects of RTD compared to the sham depletion control session. CONCLUSIONS: The summer remission experienced by SAD patients is not dependent on plasma tryptophan levels (and presumably brain serotonin function) in the same manner as that of remission after light therapy. These results conflict with those of other laboratories, perhaps because of differences in study samples.

A controlled study of light therapy in women with late luteal phase dysphoric disorder.

Previous studies suggest that light therapy, as used to treat seasonal affective disorder, may be beneficial for pre-menstrual depressive disorders. We conducted a six-menstrual cycle randomized, double-blind, counter-balanced, crossover study of dim vs. bright light therapy in women with late luteal phase dysphoric disorder (LLPDD). Fourteen women who met DSM-III-R criteria for LLPDD completed two menstrual cycles of prospective baseline monitoring of pre-menstrual symptoms, followed by two cycles of each treatment. During the 2-week luteal phase of each treatment cycle, patients were randomized to receive 30 min of evening light therapy using: (1) 10000 lx cool-white fluorescent light (active condition); or (2) 500 lx red fluorescent light (placebo condition), administered by a light box at their homes. After two menstrual cycles of treatment, patients were immediately crossed over to the other condition for another two cycles. Outcome measures were assessed at the mid-follicular and luteal phases of each cycle. Results showed that the active bright white light condition significantly reduced depression and pre-menstrual tension scores during the symptomatic luteal phase, compared to baseline, while the placebo dim red light condition did not. These results suggest that bright light therapy is an effective treatment for LLPDD.

Growth hormone response to baclofen in patients with seasonal affective disorder: effects of light therapy.

There is evidence for gamma-aminobutyric acid (GABA) dysfunction in the pathophysiology and treatment response of patients with major depression, but this has not been studied in seasonal affective disorder (SAD). Growth hormone (GH) response to a challenge with a GABAB receptor agonist, baclofen, is considered an in vivo index of hypothalamic GABAB receptor function in humans. To explore the role of GABAB receptor function in SAD, we compared the GH response to baclofen challenge in 15 patients with SAD and 20 matched healthy controls. Of the 15 patients with SAD, 14 had repeat baclofen challenge following 2-week treatment with light therapy. The results showed that baclofen administration led to a significant increase in GH release both in patients with SAD and normal controls. There was no significant difference in the GH response to baclofen between the two groups. Furthermore, 2-week treatment with light therapy did not significantly alter the baclofen-induced GH response in patients with SAD, in spite of a clear therapeutic effect. The results of this study suggest that hypothalamic GABAB receptor function, as measured by baclofen induced GH release, is not altered in patients with SAD or by light therapy.

Seasonality of symptoms in women with late luteal phase dysphoric disorder.

OBJECTIVE: Both late luteal phase dysphoric disorder (LLPDD) and seasonal affective disorder are cyclical disorders often manifested by "atypical" depressive features. The goal of this study was to determine whether patients with LLPDD demonstrate substantial seasonal variation in symptoms. METHOD: Consecutive female patients attending a subspecialty clinic in a university teaching hospital were assessed by means of DSM-III-R criteria. All subjects completed the Seasonal Pattern Assessment Questionnaire, modified to include items on the seasonality of premenstrual symptoms. The results were compared with those of a group of female nonclinical subjects (N = 50). RESULTS: One hundred patients met the DSM-III-R criteria for LLPDD. Compared to the nonclinical group, the LLPDD patients had a significantly higher mean global seasonality score (an index of seasonality of mood and vegetative symptoms) and a significantly higher rate of seasonal affective disorder (38% versus 8%) as determined by Seasonal Pattern Assessment Questionnaire criteria. Twenty-five percent of the LLPDD group rated their seasonal variation in premenstrual symptoms as marked or severe, while 30% considered seasonal changes in overall symptoms to be a marked or severe problem. CONCLUSIONS: These results suggest that patients with LLPDD have substantial seasonal patterns in mood and premenstrual symptoms. These seasonal patterns have implications for the clinical assessment and treatment of LLPDD. For example, light therapy may be beneficial for women with seasonal worsening of LLPDD.

Growth hormone response to sumatriptan (5-HT1D agonist) challenge in seasonal affective disorder: effects of light therapy.

To explore the role of serotonergic system in seasonal affective disorder (SAD), we compared growth hormone (GH) responses to a challenge with a novel 5-HT1D receptor agonist sumatriptan between 11 patients with SAD and nine healthy controls. Of the 11 patients with SAD, nine had repeat sumatriptan challenge following treatment with light therapy. The results showed that GH responses were significantly blunted during winter depression in patients with SAD compared to healthy controls. The GH responses normalized following treatment with light therapy to similar levels in controls. The results of this study provide a support for the role of serotonergic system in pathophysiology of SAD and in the mechanism of action of light therapy.

L-tryptophan augmentation of light therapy in patients with seasonal affective disorder.

OBJECTIVE: Up to one-third of patients with seasonal affective disorder (SAD) do not have a full response to light therapy. Given the evidence for serotonergic dysregulation in SAD, we examined the possible role of l-tryptophan as an augmentation strategy for nonresponders and partial responders to light therapy. METHOD: Eligible drug-free patients meeting DSM-IV criteria for SAD were treated for 2 weeks using a standard morning light therapy regimen (10,000 lux cool-white fluorescent light for 30 minutes). Partial and nonresponders were treated for 2 weeks with open-label l-tryptophan (1 g 3 times daily) while light therapy was continued. Ratings at baseline and follow-up included the 29-item Structured Interview Guide for the Hamilton Depression Rating Scale, SAD version (SIGH-SAD) and the Clinical Global Impression (CGI) scale. RESULTS: Sixteen patients began the l-tryptophan augmentation phase. Two patients discontinued medications within 3 days because of side effects. In the 14 patients completing treatment, the addition of l-tryptophan resulted in significant reduction of mean depression scores. Nine of 14 patients (64%) showed very good clinical responses to combined treatment and minimal side effects. CONCLUSION: This open-label study suggests that l-tryptophan may be an effective augmentation strategy for those patients with SAD who show limited or poor response to bright ligh therapy. Further placebo-controlled studies are warranted to demonstrate efficacy.

Effects of rapid tryptophan depletion in patients with seasonal affective disorder in remission after light therapy.

BACKGROUND: Previous studies show that rapid tryptophan depletion reverses the effects of therapy with serotonergic, but not noradrenergic, antidepressant drugs in patients with remitted nonseasonal depression. The objective of this study was to investigate the effects of rapid tryptophan depletion in patients with seasonal affective disorder (SAD) that was in clinical remission after light therapy. METHODS: Patients who met DSM-III-R criteria for recurrent major depressive episodes, seasonal (winter) pattern (equivalent to SAD), were treated with a standard course of light therapy. Ten patients with SAD in clinical remission after light therapy underwent rapid tryptophan depletion in a placebo-controlled, double-blind crossover study. Behavioral ratings and plasma tryptophan levels were obtained before and after rapid tryptophan depletion. RESULTS: Plasma total and free tryptophan levels were significantly reduced to 20% of normal levels by the rapid tryptophan depletion. The depletion session resulted in significant increases in depression scores compared with the sham control session. Six of 10 patients had a clinically significant relapse of their depression following the tryptophan depletion session. CONCLUSIONS: Rapid tryptophan depletion appears to reverse the antidepressant effect of bright light therapy in patients with SAD. This suggests that the therapeutic effects of bright light in SAD may involve a serotonergic mechanism.

Ascending catecholamine pathways and amphetamine-induced locomotor activity: importance of dopamine and apparent non-involvement of norepinephrine.

Stereotaxically placed intracerebral microinjections of 6-hydroxydopamine (6-OHDA) were used to produce selective and extensive lesions of either the dopaminergic nigro-neostriatal bundle or the dorsal and ventral noradrenergic projections in the rat. The extensive damage of the noradrenergic pathways which is typically obtained after intranigral 6-OHDA injections was completely prevented by pretreatment with desipramine. Extensive depletions (85-95%) of norepinephrine (NE) in the hypothalamus, cerebral cortices and hippocampi failed to influence either spontaneous or D-amphetamine-induced locomotor activity. Neither the time course of the amphetamine response as measured by photocell cages nor the qualitative nature of the response as determined by direct observation was significantly altered by these lesions. In contrast, selective depletion (92%) of neostriatal dopamine (DA) after intranigral 6-OHDA injections severly reduced but did not abolish amphetamine-induced hyperkinesia. At the highest dose studied (2.0 mg/kg) these animals showed an initial increase in activity but, unlike controls, failed to maintain this level. This response was probably mediated by the small remaining stores of DA in the neostriatum. Pimozide (0.5 mg/kg) also severely attenuated but did not abolish amphetamine-induced locomotor activity. These data are consistent with the view that ascending DA projections are a critical substrate for amphetamine-induced hyperkinesia. They furthermore suggest that ascending NE systems do not play a role in this response.

Neuroleptic-induced deficits in food and water regulation: similarities to the lateral hypothalamic syndrome.

The role of central dopaminergic mechanisms in the regulation of food and water intake was assessed by examining the effects of haloperidol and pimozide on various measures of feeding and drinking in rats. Haloperidol (0.20 mg/kg) or pimozide (0.45 mg/kg) did not significantly affect 1-hr water intake in response to 24 hrs of water deprivation, nor did they influence 2-hr food intake after 24 hrs food deprivation. However both pimozide and haloperidol significantly reduced drinking in response to injections of hypertonic saline. In addition, animals pretreated with these drugs drank less than controls in the absence of food (a measure of "non-prandial" drinking), and drank less than controls when the water was adulterated with quinine (a measure of "finickiness"). These drugs also significantly reduced food intake in response to injections of insulin and attenuated amphetamine anorexia. These deficits are similar to those observed after electrolytic lesions of the lateral hypothalamus or after 6-hydroxydopamine lesions of the substantia nigra. Because haloperidol and pimozide block central dopaminergic receptor sites, the present findings are consistent with the hypothesis that part of the lateral hypothalamic syndrome is the result of damage to the dopaminergic nigro-neostriatal projection. Finally, the data suggest that the changes in feeding and drinking induced by haloperidol and pimozide reflect genuine homeostatic deficits rather than being due to a neuroleptic-induced motor dysfunction.

Attenuation of amphetamine-induced motor stimulation and stereotypy by 6-hydroxydopamine in the rat.

1. In accord with previous reports, intraventricular administration of 6-hydroxydopamine (250 mug) to rats did not influence spontaneous locomotor activity. Neither was the stereotyped behaviour seen after high doses of (+)-amphetamine (5 mg/kg) changed by this treatment. Increases in motor activity induced by (+)-amphetamine (0.5 and 1.0 mg/kg) were significantly reduced after 6-hydroxydopamine.2. When 6-hydroxydopamine (250 mug) was administered to tranylcypromine (5 mg/kg) pretreated animals, spontaneous activity was significantly reduced. The stimulant effects of (+)-amphetamine (0.5 and 1.0 mg/kg) were completely abolished and amphetamine stereotypy (5.0 mg/kg) was absent or reduced after this treatment.3. Bilateral injections of 6-hydroxydopamine (10 mug) into the substantia nigra abolished the more pronounced features of amphetamine stereotypy. However, although significantly reduced, amphetamine-induced locomotor stimulation was observed in these animals. Spontaneous activity was also reduced.4. These observations suggest that dopaminergic nigro-striatal neurones mediate some of the stimulant effects of amphetamine as well as being of critical importance in amphetamine-induced stereotypy. However, other catecholaminergic neurones also appear to be involved in amphetamine motor stimulation. The results are consistent with the view that amphetamine exerts its behavioural effects indirectly through its action on brain catecholamines.