On: Serotonin booster leads to increased functional brain connectivity

[svnt]

>> provide no consistent evidence of there being an association between serotonin and depression, and no support for the hypothesis that depression is caused by lowered serotonin activity or concentrations

I did not read your paper, but believe parent is making a different claim: it is not lowered serotonin levels or reduced activity, but an increase in receptors (perhaps a proxy for expected serotonin levels) that is causing the problem.

If this paper is specifically addressing serotonin levels or movement I can’t see how it could address receptor density.

[simiones → svnt]

The paper is specifically claiming there is just no association between serotonin activity and depression. By my understanding, that should include increased/decreased receptors, reuptake, breakdown etc.

[svnt → simiones]

Ok, I read the paper. Here is the most pertinent part on receptors:

> Fourteen different serotonin receptors have been identified, with most research on depression focusing on the 5-HT1A receptor [11, 34]. Since the functions of other 5-HT receptors and their relationship to depression have not been well characterised, we restricted our analysis to data on 5-HT1A receptors [11, 34].

So they reviewed two 2016 meta analyses of one out of fourteen known receptors involved in the process.

> Both meta-analyses were based on studies that predominantly involved patients who were taking or had recently taken (within 1–3 weeks of scanning) antidepressants or other types of psychiatric medication, and both sets of authors commented on the possible influence of prior or current medication on findings.

So both meta analyses were very sensitive to temporally proximate relevant medication use.

Of the two receptor analyses:

> one analysis was of very low quality [37], … and one was strongly influenced by three studies and publication bias was present [38].

This is about as little (and sadly as much) as one could do to address receptors, and about as far from a dismissal of association of receptor count and depression as it is possible to get.