They say whatever doesn't kill you makes you stronger, but how well does this home-baked philosophy stand up to our understanding of bipolar disorder? Well, not at all according to the kindling model of mood disorders.
The issue of relapse has never fully been understood beyond some of the factors known to, or suspected of, acting as triggers. One thing we know about mood disorders is that once they start people do not develop a tolerance to them. On the contrary, the evidence points to a likelihood of increased sensitivity to events or situations likely to trigger a relapse. This shouldn't be confused with the capacity to cope with or possibly even head off an event through insight and experience.
Life stress and biological susceptibility are thought to play important roles in the onset of mood disorders. The kindling model suggests that the first ever episode of mood disorder is more likely to be associated with major stressors than are episodes occurring later in the course of the illness. The basis of this assertion comes from clinical observations of animal studies and in particular the effects of electrical stimulation to the limbic area of the brain. Early experiments into epilepsy found that a fairly high intensity electrical discharge was required to induce a fit. Over time it was found that less and less was required. Such experiments have been interpreted as showing brain sensitivity becomes heightened as a result of focused stimulation.
A look at the medical data tells us that up to 80 percent of people who suffer the symptoms of a mood disorder like depression are likely to experience it again and with increased frequency. The longer the period without relapse and the milder the symptoms, the more optimistic we can be about their future.
Returning to first principles, there is a good amount of evidence to suggest that people who react to stress in depressive or manic ways do not increase their stress tolerance. The kindling model suggests that ever weaker stressors and adverse life events are then sufficient to trigger a relapse. Over time, it is suggested, the person may even become less sensitive to recognizing external triggers as potential threats to relapse.
The kindling model offers some interesting thoughts for future research. We need to know much more about the nature of major life events and how these affect stress sensitivity, for example. At the intuitive level however it seems to make sense to focus on treating first case depression or mania with much greater care and diligence.
Monroe, S M & Harkness. K L (2005). Life stress, the 'kindling hypothesis', and the recurrence of depression; Considerations from a life stress perspective. Psychological Review, 112,417-445.
Published On: February 16, 2011
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