Why do antidepressants take so long to work?



For example is thought to work after 3 weeks, any reason behind that?

In: Biology

Basically because you need a certain concentration in your blood before they can take effect which takes a while to get to. Also most psychiatrists will recommend starting at a relatively low dose and working your way up to a therapeutic dose because psych meds are notorious for having lots of side effects. Both of these add up to long times for full effects to take hold. In cases where a person may need holding over short term anti anxiety meds can be used until the antidepressants have time to kick in. Remember it’s a slow delicate process to coax brain chemistry to where it needs to be.

Many antidepressants are SSRIs (selective serotonin reuptake inhibitor), which is to say they are medications that block the destruction of serotonin which is naturally produced in the brain. This acts to increase the amount of serotonin in the brain but even though the SSRI may act basically immediately it takes time for the body to produce more serotonin to reach therapeutic levels.

It’s not completely a drug blood level thing. It takes a while for a person’s thoughts and perceptions to change.
People with Bi-Polar disorder can get manic off of a single dose.

We don’t know for sure. The mechanism of action for most psych drugs is not very well understood (and neither is anything else about the brain).

But one way to think about it: depression is a fairly stable state. Someone who is depressed can stay depressed for a long time even if there’s occasional good things happening, which means if you *are* depressed you’ll tend to *stay* depressed, at least in the short term. (Most depressive episodes last months to a year or two.)

Antidepressants, however they work, are thought to act at least in part to reduce the stability of the depressed state. That’s part of why psychedelics (which are believed to basically make the brain “less stable” and more willing to shift into weird states) are being researched as possible treatments for it.

But even as the state becomes less stable, it still takes time for the brain to find its way out of that state and to find a new, healthier stable state elsewhere.