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Biomedical subjects

T Partonen

Publications and source records attributed to T Partonen.

At least 37 records · Page 2Linked to original sources
PubMed1998

One pacemaker in seasonal affective disorder.

Patients with winter seasonal affective disorder (SAD) often have abnormalities in the resetting of their circadian clock. The circadian cycle appears to be variable across days among these patients, deviating from the exact 24 hours, and peaking at unstable times. The findings suggest that the mean free-running circadian period is longer in winter SAD patients compared to healthy subjects. It is hypothesized that there would be a singular circadian pacemaker in the patients against the two pacemakers in healthy subjects.

Chronobiology Phenomena↗
PubMed1998

Vitamin D and serotonin in winter.

Calcitriol accumulates in the nuclei of adrenal medullary cells, stimulating the tyrosine hydroxylase gene expression. The transcription of the CREM gene is induced by adrenergic input to the pineal gland at night. Depending on the photoperiod of the prior night length, the CREM gene is either subsensitive or supersensitive to induction. Guided by the memory of past photoperiods, the induced changes in melatonin synthesis may mediate either the inhibitory or stimulatory effects on bodily functions. Calcitriol might inhibit the binding of melatonin to the nuclear retinoid Z receptors, which would result in the increased serotonin levels. Serotonin synthesis is hypothesized to be dependent on the duration of light exposure the previous summer.

Humans↗
PubMed1998

A developmental approach to severe depression.

Reduced rapid-eye-movement (REM) sleep latency and increased REM sleep activity are associated not only with increased risk of recurrent depressive episodes but also with shortened time to the onset of subsequent episodes. Increased REM sleep activity might be a sign of attempt to excite the photic-responsive brain regions during the night, and there is a negative correlation between regional blood flow in the dorsolateral prefrontal cortex and REM sleep. The relative deactivation of the dorsolateral prefrontal cortex as a result of a developmental abnormality could explain the increased REM sleep activity during the first half of the night and the subsequent terminal insomnia among depressed subjects.

Animals↗
PubMed1998

Dependence of the variation in alertness on the pineal gland.

There is a diurnal variation in the pineal serotonin content, with a maximum at 7-8 h after the onset of light and a minimum at 3-4 h after the onset of darkness in rats. The levels of serotonin and melatonin can rapidly be altered by changing the level of ambient light. The diurnal changes in serotonergic activity are hypothesized to counteract two phenomena. First, the increased levels of serotonin would decrease the high propensity to drowsiness in the afternoon. Second, the decreased levels of serotonin would also decrease the high propensity to waking up at night, which occurs because of decreased melatonin secretion.

Animals↗
PubMed1998

Psoralens in association with seasonal affective disorder.

The pathogenesis of seasonal affective disorder (SAD) has been attributed to abnormal melatonin metabolism. Perorally administered psoralens increase the daytime levels of melatonin via the competitive inhibition of hepatic melatonin metabolism. Some findings among SAD patients are parallel to those observed after the administration of a psoralen in healthy subjects. It is hypothesized that there may be a circulating psoralen-like substance which affects SAD patients under a low level of illumination. Exposure to bright light during the daylight period would normalize the abnormal effect independently of the season.

5-Methoxypsoralen↗
PubMed1998

Randomized trial of physical exercise alone or combined with bright light on mood and health-related quality of life.

BACKGROUND: So-called atypical depressive symptoms (carbohydrate craving, prolonged sleep, weight gain, increased appetite) frequently emerge in association with low illumination to which people are ordinarily exposed indoors, or even outdoors at extreme latitudes in wintertime. Our objective was to analyse the effect of physical exercise alone or combined with bright light on mood and the health-related quality of life during winter. METHODS: We carried out a randomized controlled trial on 120 indoor employees in southern Finland between November and January. The subjects were allocated to supervised fitness training under bright (2500-4000 lx) or ordinary (400-600 lx) light conditions in a gym 2-3 times weekly for 8 weeks, or supervised relaxation training once a week over the same period as active placebo. We collected questionnaire data on the changes in mood and health-related quality of life after 4 and 8 weeks of training, and after 4 months follow-up. RESULTS: Fitness training in bright light resulted in greater relief from atypical depressive symptoms and more vitality than in ordinary room light. Compared with relaxation alone, the former regime improved general mental health and social functioning in addition to the improvement in depressive symptoms and vitality, whereas the latter only increased vitality. CONCLUSIONS: Supervised physical exercise combined with exposure to bright light appears to be an effective intervention for improving mood and certain aspects of the health-related quality of life in wintertime. This effect appears unrelated to the history of season-dependent symptoms, being noticeable among healthy individuals.

Adult↗
PubMed1997

Suppression of melatonin secretion by bright light in seasonal affective disorder.

Eleven patients with winter seasonal affective disorder and 10 healthy controls were exposed to light of 3300 lux for 5 min and for 1 hour respectively on consecutive evenings at 22:00 hours during winter and summer. In the winter, the measurements were undertaken both before and after the treatment with bright light for 2 weeks. In the summer, there was no treatment. Melatonin concentration in saliva and subjective sleepiness were measured at 22:00 and 23:00 hours on each test. There was no significant difference in the suppression of melatonin in response to the light tests between the patients and the controls. Exposure to light reduced the level of subjective sleepiness more among the patients compared to the control subjects. This reduction was not associated with the change in melatonin secretion nor the improvement in depressive symptoms.

Adult↗
PubMed1997

Pavlovian conditioning may partly explain the effects of light therapy.

Explicit pairings of a non-photic stimulus and exposure to light are capable of inducing behavioural responses that are characteristic of the resetting of the circadian system by light as well as cellular effects in the neural regions that are normally activated only by light. The setting of light therapy as used for treatment of winter seasonal affective disorder resembles that of Pavlovian conditioning. The conditioning may provide a rationale for the sustained therapeutic response to light treatment observed to last for the rest of the season in some of the patients treated with light.

Circadian Rhythm↗
PubMed1996

Moclobemide and fluoxetine in treatment of seasonal affective disorder.

Of a total of 581 consecutive depressed subjects attending psychiatric services of 6 centres in Finland, 183 patients were eligible and completed a 6-week randomised double-blind trial with either moclobemide or fluoxetine. Of these, 32 (17.5%) patients met the DSM-III-R criteria for mood disorder with a seasonal (winter) pattern and 19 patients (10.5%) met the original criteria for seasonal affective disorder (SAD). There were no significant difference in the antidepressive response to the treatment between the patients with SAD and other depressive disorder. The treatment of 6 weeks with either moclobemide (300-450 mg daily) or fluoxetine (20-40 mg daily) resulted in a full remission in 15 (52%) patients with SAD and in 44 (37%) patients with other depressive disorder. Altogether, 23 (79%) and 83 (70%) patients, respectively, got significant benefit from the treatment. The improvement in the health-related quality of life in terms of ability to work was significantly more extensive in the patients with SAD assigned to receive moclobemide compared with the other depressive patients allocated to the same medication. Subjects who in addition met the operational criteria for atypical depression were equally distributed into the SAD and other depressive patient groups.

Adult↗
PubMed1996

Effects of bright light on sleepiness, melatonin, and 25-hydroxyvitamin D(3) in winter seasonal affective disorder.

Sixteen patients with winter seasonal affective disorder and 13 healthy controls were exposed to 3300 lx of cool-white fluorescent light for either 1 hour or 15 min in the morning for 2 weeks during the winter. Subjective sleepiness, melatonin concentration in saliva, and serum 25-hydroxyvitamin D(3) concentration were measured before and after the 2-week trial as well as the following summer when the patients were well. There were no significant differences in the baseline values between the patients and healthy subjects. No significant differences in the outcome measures were observed in the patients or the controls in the two groups of each after the trial. The exposure to bright light resulted in a significant decrease in subjective sleepiness early in the evening in the patients but not in the control subjects. The reduction of depressive symptoms was associated with the decrease in subjective sleepiness but not with the changes in the melatonin or vitamin D concentrations.

Adult↗
PubMed1996

Dopamine and circadian rhythms in seasonal affective disorder.

In seasonal affective disorder, there is evidence of both increased and decreased dopaminergic transmission in the central nervous system. Bright light treatment appears to normalize these abnormalities among the patients. Dopamine is suggested to have a direct effect on heat loss via the vascular system, in addition to its capability of resetting the circadian system by changes in both heat production and heat loss. Therefore, impaired dopamine availability may result in a decreased heat loss response to an endogenous thermal challenge as well as abnormalities in the generation of circadian rhythms in some patients with seasonal affective disorder.

Body Temperature Regulation↗
PubMed1996

Possible pathophysiological mechanisms regulating food intake in seasonal affective disorder.

Noradrenaline, estrogen, neuropeptide Y and galanin are all involved in regulation of eating behaviour. Based on a recent case report on seasonal affective disorder (SAD), there is evidence of decreased insulin sensitivity. Reduced insulin sensitivity may increase the transcriptional activity of the neuropeptide Y gene in the medial basal hypothalamus and subsequent ingestion of food. Decreased availability of estrogen may also increase the levels of neuropeptide Y, leading to decreased release of noradrenaline from the ventromedial hypothalamus. The increased noradrenaline content may increase the concentration of galanin, which will decrease the circulating levels of insulin and increase the pace of transcription of the neuropeptide Y gene. Among some SAD patients, it is possible that the sustained ingestion of high-fat diet will rather activate the transcription of the neuropeptide Y gene than deactivate it, indicating a defect in macronutrient selection.

Animals↗
PubMed1996

Prevention of winter seasonal affective disorder by bright-light treatment.

In patients with winter seasonal affective disorder (SAD) the onset of a depressive episode is probably associated with the decreasing amount of light during the autumn. A highly predictable onset of a recurrent depressive episode with seasonal pattern provides a rationale for testing the efficacy of bright-light treatment as a preventive measure. Twelve out-patients with winter SAD were assigned to start bright light treatment either when they were well, or not to start it until the first symptoms of depression had already emerged. The severity of depressive symptoms was prospectively rated for a parallel randomized comparison. Bright light given well in advance of the emerging symptoms prevented a depressive episode. Clinical remission was significantly more frequent in the former subgroup of the patients in January and in March. To sum up, bright light can be successfully administered as prophylactic treatment for the prevention of winter SAD.

Adult↗
PubMed1996

Seasonal variation in bipolar disorder.

BACKGROUND: In patients with bipolar disorder, admissions for manic and depressive episodes frequently display a seasonal pattern. We examined this variation and compared the patterns with the seasonal admission rates for schizophrenia. METHOD: Patients with bipolar disorder or schizophrenia were identified from the Finnish Hospital Discharge Register of in-patient admissions to all psychiatric hospitals during the years 1969-91. They were included in the analysis if the first admission had occurred before 30 years of age. A total of 295 bipolar patients were found, and a sample of 295 schizophrenic patients was randomly selected for comparison. RESULTS: There was no seasonal variation among all hospital admissions for bipolar disorder or schizophrenia. However, the first admission for a depressive compared with a manic episode of bipolar disorder occurred significantly more often in the autumn (33% v. 21% respectively). The peak difference occurred during the week after the autumnal equinox in September. CONCLUSION: Our findings suggest that there is no seasonal variation in bipolar disorder, although in some patients the clinical course might be influenced by the autumn, as far as the likelihood of a first admission for depression is concerned.

Adult↗
PubMed1996

Patients excluded from an antidepressant efficacy trial.

BACKGROUND: The impact of exclusion criteria on antidepressant trials is rarely investigated and poorly understood. We describe specific reasons for exclusion from a double-blind comparative trial and analyze the selection procedure and its impact on treatment outcome. METHOD: A 6-week randomized double-blind trial for depressive disorders recruited patients through outpatient psychiatric services, private offices, and health care centers. Of the 612 consecutive patients interviewed for a diagnosis according to DSM-III-R, 209 (34%) finally entered the trial. RESULTS: 86% of the included patients had no comorbid psychiatric disorder, whereas a third of those excluded had at least one (p < .00001). Patients were excluded for having chronic alcohol or drug misuse (17%), receiving antidepressant drugs (15%), or having physical problems precluding their ability to take either of the drugs studied (14%). Some patients could not be included because of a referral to other modes of treatment (19%) or organizational difficulties (16%). The excluded patients less often suffered from major depressive disorder than those who were included in the trial. In particular, patients excluded because of suicidal thoughts or intent more often had a history of previous major depressive episodes (p = .006) compared with the included patients. The most important sociodemographic factors related to exclusion from the trial were male sex and unmarried status. CONCLUSION: Patients with previous depressive episodes or comorbid disorders were more likely to be excluded from the antidepressant efficacy trial. Data on the efficacy of antidepressant drugs on this patient population are still only infrequently obtained.

Adult↗
PubMed1995

A mechanism of action underlying the antidepressant effect of light.

In patients with winter seasonal affective disorder (SAD), delayed and reduced responses to corticotropin-releasing factor (CRF) have been observed. Bright light treatment has been shown to normalize these responses. In depressed patients, there is increased CRF activity in the evening during the normally quiescent period between 19.30 and 22.00 hours. In patients with winter SAD, the level of subjective sleepiness is increased in the evening between 20.00 and 21.00 hours. In the latter group of patients, the CRF activity may be increased in the evening and associated with the increased level of subjective sleepiness. This increased activation is suggested to be normalized by bright light treatment, acting primarily on neurons of the paraventricular nucleus of the hypothalamus.

Adrenocorticotropic Hormone↗