If this isn’t a goady comment, a very quick read of a Wikipedia entry would tell you how they work. Every antidepressant is in a category named after the chemical it affects, to tell you “what it does.” For example, the most numerous category is, I believe, the SSRIs. As I said, the key is in the name: they are selective SEROTONIN reuptake inhibitors. The article on SSRIs says right at the beginning that these drugs, such as Sertraline, limit the réabsorption, or reuptake, of the chemical serotonin, so the person will have more serotonin (it’s a little more complex than that - it forces the serotonin to stay longer in a certain cell gap). You should then be able to read how serotonin works to understand why these anti-depressants, in particular, aren’t “happy pills.”
Serotonin is NOT a happiness chemical, nor does it cause amnesia, or lack of emotions - so you won’t be floating on a cloud, or forget what made you sad, or be incapable of a full range of emotions, though the hope is that it will stop major depressive states. It just simply does not make people “happy.” Not even like fresh air does. That’s the chemical dopamine. So it is believed someone with more serotonin will experience less anxiety, possibly less psychosis, not more happiness. This is why most people on anti-depressants explain it as “keeping them even” or stopping them from reaching a deep depressive or anxious state, versus making them feel even a slight “happy” lift, like they might feel at some point from fresh air or seeing a friend (note: these things don’t erase depression; I’m just saying that for some people, sometimes, they can boost dopamine a bit).
The second most common class of anti-depressants, SNRIs, are serotonin-norepinephrine reuptake inhibitors, so the exact same thing but with both serotonin and norepinephrine. Again, you can just read the Wikipedia article on what norepinephrine is, or on SNRIs.
We do not have a way to introduce dopamine for neurological use. The only dopamine for medical use is by vein, has a very short period of working (half-life), doesn’t affect the brain so much as the heart, and has some bad side effects (possible kidney damage). If we had TRUE anti-depressants that could somehow raise your neurological dopamine in a manner that didn’t lead to a dangerous rebound, I imagine they would be worth trillions of pounds and save thousands of lives. As it is, SSRIs are the best we have and they DO save a lot of lives - think of it as them removing some of the depression and anxiety, not overwriting it with happiness.
Studies have shown that those with anxiety have less serotonin, which is why it makes sense that: these drugs work, and we should take them. The real question is: WHY are people anxious, or depressed? As many people have commented, they don’t have a bad life or bad job or bad treatment from others, yet still need anti-depressants. Some psychologists are beginning to posit it’s because humans have reached a point where what we expect from modern life is simply pushing ourselves too far - how many women post on here that have no time for any personal hobbies or time to themselves? It’s impossible to keep filling from an empty cup without eventually feeling anxious and depressed. The idea that a job, a family, and no one treating you badly should be enough to make up a life is perhaps the problem. And the idea that “not badly” is good enough treatment may be part of it, too - how many times have women posted on here that are married to men who are just awful, but they seem to think since they aren’t being abused or treated TOO badly, that the treatment is acceptable? And yes, some people could have an absolutely perfect life - be healthy and wealthy and with a loving family and still feel depressed, because we’re talking about chemical imbalances, and that’s what anti-depressants treat.