You've just come back from Iraq, and your friends have taken you out to a club to welcome you home, and to remind you that you went overseas to put your life on the line in defense of Axe Body Spray and Nicki Minaj remixes. Strobe lights are flashing in your eyes, people waving glow sticks are bumping into you from all sides and the thumping of the club's subwoofers is vibrating your brain against the side of your skull. Suddenly, a switch is thrown in your mind and you're back in Iraq. The desert night is lit by tracer fire and earth-shaking explosions, and you are surrounded by people with light sabers.
You're having a flashback. Quick, grab hold of one of those evil Jedi and fish through their pockets for some MDMA, more commonly known as Ecstasy (don't worry, they almost certainly have some).
And we're positive that they won't notice your hands down their pants.
You see, Ecstasy has been shown to help treat people with post-traumatic stress disorder. The reason for this is actually the same reason that the drug is popular recreationally: It releases large amounts of the chemicals serotonin and oxytocin in your brain, making you relaxed and euphoric. For the people in the club, this means they will have a good time and probably have sex with a stranger. For PTSD sufferers like yourself, this means life gets a whole lot less stressful.
"For me, it means I'm going to dong your grandma's butthole, and she's going to thank me for it."
MDMA also allows PTSD patients to relive their experiences more easily while in therapy, which is crucial to overcoming the disorder. Ecstasy lets the sufferers do so without being overwhelmed, by activating the area of the brain responsible for controlling fear and stress. Over time, this results in long-term reduction of fear, allowing the victims to get on with their now dubstep-filled lives.
Let's say for argument's sake that you're overweight. Also, you can't pay attention at school or work, and as a result your performance is steadily declining, so you're eating Butterfingers wrapped in bacon to help cope with your frustrated depression. But no matter how bad things get, you resist the urge to take drugs, even though grandma insists that the meth she makes is the bomb.
Finally, you go to the doctor to ask if anything can be done to control your crippling inattention and overeating. He scratches his chin and says, "Have you tried a little thing I like to call methamphetamine?"
"I promise you that by this time tomorrow, you'll be calling me 'Dr. Chad Feelgood.'"
OK, taking meth to lose weight isn't that hard to believe -- after all, anorexia and dramatic weight loss are two of the primary telltale symptoms of chronic meth use, so why not harness that power like Ellen Burstyn in Requiem for a Dream? So Desoxyn, the purest form of meth, is given to obese people for fast short-term weight loss. It's only prescribed as a short-term treatment for obvious reasons (meth is highly addictive and catastrophic to your well-being). It's also pretty uncommonly used in this way, as it's really only prescribed when all other treatments fail ("other treatments" here meaning "vegetables and jogging").
"Mrs. Johnson, all your boy needs is some discipline, a lot of fresh air and a dollop of straight meth."
But even stranger, Desoxyn is prescribed by doctors all over the United States to treat ADHD. Considering that sufferers of ADHD typically exhibit symptoms of jitteriness and inattentiveness, and that meth also causes all of those things, you'd think the first dose would cause the patient's brain to speed up until he was living in bullet time.
But nothing with the brain is simple, and meth (as well as other stimulants) help regulate brain chemicals called neurotransmitters. At least, that's what happens when the dosage is carefully controlled by a medical professional who can monitor the results. In general, you should not attempt to self-medicate any medical problem with any substance bought in an alley from a bunch of bikers standing around a burning trash barrel.
For more bad things that actually help you, check out 5 Hallmarks of Bad Parenting That Are Actually Good for Kids and 5 Surprisingly Positive Side Effects of Horrible Diseases.