Serotonin: the most misunderstood neurotransmitter

(a thread)

In popular culture serotonin (5HT) is generally viewed as something that causes happiness, usually seen in the form of memes about the lack thereof

This is likely based on what's known as the Serotonin Model of Depression, which is the idea that depression and other mental illness is the result of serotonin deficiency

Until recently this has been the predominant theory as to what causes depression

This theory has resulted in the use of SSRIs (selective serotonin reuptake inhibitors) as the main treatment for depression, as they increase serotonin production

The odd thing is that in double-blind studies they are barely distinguishable from placebo, and take months to work

Another reason we equate serotonin with happiness is psychedelics, which all affect at least a few of the 5HT receptors, and show antidepressant effects long after the trip ends

In fact, serotonin receptors were first discovered when scientists were studying the effects of LSD

But if both SSRIs and psychedelics affect serotonin receptors why does one works for months and the other take months to work?

Well, maybe serotonin isn't the main issue here

Both classes of drugs have been shown to have another effect in common: they cause neurogenesis (brain cell growth)

Psychedelics also decrease levels of the peptide dynorphin, which has been linked to PTSD and depression

These may be the real reasons for their positive effects

So what does serotonin really do?

Well it does play a role in mood, but that's becuase higher levels of it causes release of the real major players like dopamine + endorphins

If serotonin levels are stable this effect does not occur as much, hence why SSRIs have little effect

It is also one of the most common neurotransmitters on earth, it is present in all animals and some plants, and many baceteria have even been shown to have receptors for it

In humans it affects dozens of functions including appetite, sleep, wound healing, and digestion

However, our best research shows more and more that it is NOT the sole cause of depression

So what is?

Only time will tell, but we're making amazing progress and I think within the next decade or two we will have a far better understanding

Thanks for reading