Posted by Maxime on May 19, 2005, at 7:49:36
Insomnia and Depression
QuestionHow can insomnia in the long term produce depression?
Expert Response from Karl Doghramji, MD
Professor of Psychiatry, Jefferson Medical College, Philadelphia, Pennsylvania; Director, Sleep Disorders Center, Thomas Jefferson University, Philadelphia, PennsylvaniaA number of long-term demographic studies have indicated that there is a longitudinal relationship between insomnia and depression.[1-5] For example, one study showed that current insomniacs carry a high likelihood of developing depression in the future.[1] Ford and Kamerow,[2] excerpting the National Institute of Mental Health (NIMH) Epidemiological Catchment Area Study results, noted that, over a 1-year period, individuals who had no evidence of psychiatric conditions other than insomnia at study outset were much more likely to develop new major depression after 1 year when the insomnia persisted compared with those in whom it resolved. These and similar studies have supported theories of a causal link between insomnia and major depression, a link in the direction of the former to the latter. Such theories have been supported by the high comorbidity of the 2 conditions and shared neurophysiological findings, such as cerebral cortical hyperarousal. Richardson and Roth[6] have proposed, for example, that increased activity of corticotropin-releasing factor (CRF) neurons innervating the noradrenergic neurons of the locus coeruleus is responsible for primary insomnia. CRF regulation has been extensively implicated in the pathogenesis of depression as well.[7] Possibly, therefore, insomnia, especially the persistent variety, enhances underlying vulnerability to depression.
The existence of a causal link between insomnia and depression raises the intriguing question of whether effective management of insomnia could offer an opportunity to prevent the future emergence of depressive disorders. However, no empirical evidence exists to support such an understanding. Indeed, the available data suggest that alternative explanations can also be made regarding the link between insomnia and depression. For example, one of the longitudinal studies cited above also shows that current insomnia enhances the risk not only for future depression, but also for substance abuse and anxiety disorders.[1] Another also indicates that hypersomnia is even a stronger predictor of future depression than insomnia.[2] Taken together, these findings suggest that, even if a causal link were to exist, it is not confined to insomnia and depression, but may involve many other conditions as well.
Finally, a causal link does not have to be posited to explain these findings. Indeed, these findings are equally well, if not better, explained by the understanding that insomnia represents a symptom of an emerging depression or other psychiatric disorder, which has yet to reach syndromal levels. In this explanation, insomnia does not represent an autonomous condition, but a symptom of an underlying psychiatric disorder. Such an explanation does not diminish the importance that insomnia may play in psychiatric disorders. Indeed, it emphasizes the importance of properly identifying insomnia in medical populations, because its existence and persistence suggest that the patient should be monitored more carefully for the emergence of a psychiatric disorder in the future.
References1. Breslau N, Roth T, Rosenthal L, Andreski P. Sleep disturbance and psychiatric disorders: a longitudinal epidemiological study of young adults. Biol Psychiatry. 1996;39:411-418.
2. Ford DE, Kamerow DB. Epidemiologic study of sleep disturbances and psychiatric disorders. An opportunity for prevention? JAMA. 1989;262:1479-1484.
3. Weissman MM, Greenwald S, Nino-Murcia G, Dement WC. The morbidity of insomnia uncomplicated by psychiatric disorders. Gen Hosp Psychiatry. 1997;19:245-250.
4. Livingston G, Blizard B, Mann A. Does sleep disturbance predict depression in elderly people? A study in inner London. Br J Gen Pract. 1993;43:445-448.
5. Chang PP, Ford DE, Mead LA, Cooper-Patrick L, Klag MJ. Insomnia in young men and subsequent depression. The Johns Hopkins Precursor Study. Am J Epidemiol. 1997;146:105-114.
6. Richardson GS, Roth T. Future directions in the management of insomnia. J Clin Psychiatry. 2001;62(suppl10):39-45.
7. Pariante CM, Miller AH. Glucocorticoid receptors in major depression: relevance to pathophysiology and treatment. Biol Psychiatry. 2001;49:391-404.
poster:Maxime
thread:499779
URL: http://www.dr-bob.org/babble/20050516/msgs/499779.html