In the article they cite as evidence for serotonin deficiency's depressogenic effects: "Overall, this evidence suggests that impairing serotonin function can c

In the article they cite as evidence for serotonin deficiency's depressogenic effects: "Overall, this evidence suggests that impairing serotonin function can cause clinical depression in some circumstances, but is neither necessary nor sufficient." From Wikipedia[1]: Since the 1990s, research has uncovered multiple limitations of the monoamine hypothesis, and its inadequacy has been criticized within the psychiatric community.[44] For one thing, serotonin system dysfunction cannot be the sole cause of depression; antidepressants usually increase synaptic serotonin very quickly, but it often takes at least two to four weeks before mood improves significantly. One possible explanation for this lag is that the neurotransmitter activity enhancement is the result of auto receptor desensitization rather which can take weeks.[45] Intensive investigation has failed to find convincing evidence of a primary dysfunction of a specific monoamine system in patients with major depressive disorders. The antidepressants that do not act through the monoamine system, such as tianeptine and opipramol, have been known for a long time. There has also been inconsistency with regards to serum 5-HIAA levels, a metabolite of serotonin.[46] Experiments with pharmacological agents that cause depletion of monoamines have shown that this depletion does not cause depression in healthy people.[47][48] Another problem that presents is that drugs that deplete monoamines may actually have antidepressants properties. Furthermore, some have argued that depression may be marked by a hyperseretonergic state[49] Already limited, the monoamine hypothesis has been further oversimplified when presented to the general public.[50] 1: https://en.wikipedia.org/wiki/Biology_of_depression https://en.wikipedia.org/wiki/Biology_of_depression