Smoking. I started to smoke a couple of months ago, and I usually smoke 2-3 cigs a week. I get dizzy after a cig because I'm not used to it, but cigs calm me down and make it hard for me to have retarded thoughts.
In addition to nicotine, tobacco contains a few naturally occurring MAOIs, which have an antidepressant effect. People with depression are 2-3x as likely to be tobacco users, schizophrenics have a tobacco use rate as high as 90℅, depending on what study you look at.
There are a few different theories as to why, but the one I think is likely to be the biggest factor is self medication. Even if people don't consciously make the connection that its treating mental health symptoms, they still get more positive effects from it, compared to a person with good mental health.
Low acetylcholine signalling can also cause depressive symptoms, which nicotine would help with. Just keep in mind that somewhat paradoxically, too much acetylcholine signalling can also cause very similar depressive symptoms. Exactly where that line is varies from person to person, but at some point, nicotine will go from making you focused and motivated to foggy and dull.
Cigarettes are a shit delivery mechanism. I've smoked more than my fair share, and still indulge on occasion, but they're the most niggerish form of tobacco possible.
Cigars are really nice, and contrary to what people might think, you can get some pretty decent ones for just a few bucks. US surgeon general says you can smoke 2-3/day without a statistically significant rose in cancer risk. The best (and worst) thing about cigars is that they force you to focus on them. A cigarette is something you have, a cigar is something you DO. Its an activity. You'll typically take an hour or two to go through a cigar. But its a very relaxing, almost meditative experience. Cigars are also great in social situations. There's no pressure for anyone to talk, because you can always just sit there, and enjoy a few puffs. It tends to make conversation much more natural and relaxed.
For more practical day to day use, I'm a big fan of Swedish snus. Its an oral tobacco, but has a different manufacturing process than American chewing tobacco, leading to far lower levels of TSNAs, the main chemicals in tobacco that cause cancer. No epidemiological link to cancer, and unless you already had hypertension or tachycardia, other health impacts are pretty much nonexistent. You can buy them online for a few bucks a tin, significantly cheaper than cigarettes in most states. You do have to pay like a $30 shipping fee, but if you order in bulk, it still averages out a lot cheaper than smoking. You might also be able to find it at local tobacco shops or gas stations, but selection is limited, and you'll be paying about 3-4x as much
It should be kept in mind that nicotine and its metabolites also inhibit conversion of testosterone into estradiol. This could be good or bad, depending on how heavily you aromatize. High e2 causes moodiness, and ED. But low e2 destroys libido, fucks up your cholesterol, raises risk of neurodegenerative disease, causes a very bitter mood, joint issues, insomnia, etc... I always recommend that people get bloodwork done. In my experience, mental health issues are usually a combination of many different factors, and "fixing" one of those usually isn't going to solve the problem... But if one of those factors is hormonal, or nutritional, or environmental, addressing that is going to help, and make it easier to start working on the other factors