APSS: Depression and Insomnia May Be Genetically Linked
SEATTLE, June 12 -- Insomnia and mood disorders may share a common genetic pathway, which could explain both depression and wakefulness observed in teens, researchers here said.
In a study of more than 1,400 twin pairs, about a third of those who were diagnosed with depression or anxiety also had insomnia, said Philip Gehrman, M.D., assistant professor of psychiatry at University of Pennsylvania School of Medicine, Philadelphia, who presented his findings at the annual meeting of the Association of Professional Sleep Societies...
... The twins studied were aged eight to 17, and 749 of the pairs were monozygotic twin pairs...
...Dr. Gehrman and colleagues studied 1,442 twin pairs and determined that 1.3% of the sample had depression, while 18% were diagnosed with anxiety.
Among those with either depression or anxiety, 32.4% had insomnia compared with 16.5% of adolescents who had insomnia but were free of clinical anxiety and/or depression...
A few comments. They studied adolescents. This is interesting, but it introduces a confounding variable. Those who experience onset of affective or anxiety symptoms in adolescence may not be representative of the population of persons who develop such symptoms at any point in their lifetimes. The same may be true of insomnia.
Another thing: it often is not difficult to find an apparent association between two fairly common conditions. Figuring out what, if anything, it means can be devilishly difficult. It could simply represent the uninteresting fact that once one thing goes wrong, it is more likely that something else will go wrong.
Or it could be true that insomnia presents a more specific risk factor that makes it more likely that a variable genetic vulnerability will be expressed to an extent that it becomes pathological. That hypothesis is attractive, in that it has face validity.
I sometimes think of depression as an illness involving faulty regulation of vegetative functions. That is, some with depression eat too much, others eat too little; some sleep too much, others too little; some have low energy, while others are restless. Some are exquisitely sensitive to rejection, whereas others are rather indifferent. (Rejection sensitivity is not a vegetative symptom, but the same principle applies.) It would be interesting to know if the Gehrman study data would permit association between insomnia and individual symptoms of depression. Is insomnia associated with one particular subtype of depression?
...Dr. Gehrman said he planned additional studies to investigate the loci of genes related to insomnia and to identify relevant mutations that make a young patient more likely to have insomnia...
This would be a natural follow-up study. It may tell us whether or not there is anything substantive to the association they found in the pilot study. I hope that he also follows these patients over a longer period of time, to see how well these findings hold up across the lifespan.
Comments
Of course it could be total myth, but I thought insomnia was more prevalent after you hit your 30s but I guess thinking about it a little bit more, sleeping less is something that I always thought grew with aging.
Posted by: logtar | June 16, 2009 12:16 PM
You will see references that say that the elderly are more at risk for insomnia, while others say that this is not clear. Melatonin does tend to decrease with age, but this does not necessarily mean that insomnia will increase. The bottom line is that nobody knows for sure, even though most people think it is true.
Posted by: Joseph j7uy5 | June 16, 2009 2:21 PM
It's well known that insomnia is a symptom of depression. In fact it's a diagnostic symptom in DSM-IV, and it appears on most rating scales for the severity of depression. Is this study adding anything new to that?
Posted by: Neuroskeptic | June 23, 2009 11:15 AM