Thanks for posting, Chris. I'd be interested to know how ME/CFS compares with depression on the 'Environment' point - can anybody here who's able to query the data have a look? I would *guess* that MDD would have quite a strong component that varies with zip code - e.g. see the discussion about
'shit life syndrome' on this brilliant article on Blackpool.
So, to try and answer my own question, I've had a play with the data and I think what it shows is this (my knowledge of heritability statistics is pretty much nil, so please treat with caution and I'd welcome any comments/corrections):
Chronic fatigue syndrome
Heritability, h2 = 0.575, p=0.007
Shared Environment, c2 = -0.106, p=0.464 <--no significant association, 95% confidence intervals are above and below zero
Major depressive disorder
Heritability, h2 = 0.180, p=0.006
Shared Environment, c2 = 0.181, p<0.001
Anxiety disorder
Heritability, h2 = 0.349, p<0.001
Shared Environment, c2 =0.077, p=0.013
Looking at that, it appears to me that:
- Whilst relying on insurance data may be problematic due to coding errors (e.g. depression or anxiety being misdiagnosed/miscoded as CFS), there are substantial differences between the results for each condition in aggregate;
- CFS shows a strong heritable component and no statistically significant 'shared environment' component. i.e. if two siblings have CFS, it's not because of parental influence
- This would seem to contradict, for example, any paediatric CFS study that indicates a certain parental personality is a risk factor for a child developing CFS.
- MDD and anxiety disorders do show a shared environment component, in contrast to CFS. This (to me) provides yet more strong evidence - if any were needed - that CFS is not a mood disorder, that CFS is not just a form of depression or anxiety.
- (I'll admit I was a bit surprised that anxiety disorder had such a strong genetic component - however, unlike CFS, it does still have a shared environment component as well)