Depression, symptoms and definition

Slate Star Codex consistently makes me feel bad about the quality of my most sciencey entries by blowing them away.  Here he does it with SSRIs.  One of the many, many data points he offers is that there is a very well known and consistent effect that doctors (and other observers) notice their patients acting less depressed (as measured by sleep patterns, appetite, ability to leave the house, hygiene standards, etc) well before patients report themselves feeling less depressed.

There are a lot of possible explanations for this.  One possible one is that we’ve reversed cause and effect: rather poor sleep, appetite, and executive function being side effects of depression, depression is a consequence of poor sleep, appetite, and executive function.  Moreover, it’s a delayed consequence.  One night of good sleep doesn’t even make up for a week of bad sleep, much less months.  So even if antidepressants instantly removed all the road blocks in someone’s life, it will take a while for those lack of road blocks to translate to feeling better.  Under this model, wondering why you’re still sad a week after starting anti-depressants makes as much sense as wondering why you’re still weak after two sessions of physical therapy. *   If the depression led to some choices with lasting consequences- quitting school, ending a relationship-it might well be impossible to give them back the life they would have had without depression.  That doesn’t mean the drugs aren’t working or aren’t useful, it just means they aren’t magic.

I didn’t intend this, but I think I just re-arrived at my model of depression as a symptom.

*This analogy was originally “starting a diet and being shocked you don’t immediately lose 30 pounds”, but that would reinforce the screamingly incorrect idea that diet has a simple causal effect on weight.