and anti-malarial drugs like Lariam have side-affects of aggression and psychosis:
http://www.thewashingtonnote.com/archives/000052.html
Lariam, also known as Mefloquine, can according to drug warning labels cause aggression, psychosis and suicidal tendencies. UPI's Mark Benjamin reported that none of the soldiers he interviewed recalled being informed of these potential side effects.
The report makes clear that there is still no scientifically proven connection between the aggressive, erratic, and suicidal behavior of these Special Forces units and Lariam, but there is a correlation thus far.
...more on Lariam:
http://www.ngwrc.org/index.cfm?page=Article&ID=1932 Lariam was invented by the Army's Walter Reed Institute of Research in the 1960s, which licensed it to Swiss pharmaceutical giant Hoffmann-La Roche; it has been approved for use in the United States since 1989. Increasing warnings have appeared on the official product label and now include aggression, hallucinations, paranoia and psychosis. The FDA ordered in 2003 that everyone prescribed the drug be given a written caution about potential side effects, including mental problems and reports of suicide. Fewer than 20 drugs come with mandatory written warnings.
In 2003 the Pentagon grew concerned over a spike in suicides in Iraq, where Lariam was prescribed, and sent another team from the Army Surgeon General's office to investigate. That team did not look at Lariam use, but Army officials said it was not a factor in any of the 24 suicides. In the year ending in October 2003 the Pentagon wrote 45,000 prescriptions for Lariam.
Improving the userfulness of amphetamines is a long range objective of the US military:
http://www.csmonitor.com/2002/0809/p01s04-usmi.html
Amphetamines follow a pattern that goes back at least 40 years to the early days of the Vietnam War – further back if one counts strong military coffee as a stimulant. But they're also part of a new trend that foresees "performance enhancements" designed to produce "iron bodied and iron willed personnel," as outlined in one document of the US Special Operations Command, which oversees the elite special-operations troops that are part of all the military services.
Indeed, the ability to keep fighting for days at a time without normal periods of rest, to perform in ways that may seem almost superhuman (at least well beyond the level of most people in today's armed services), is seen by military officials as the key to success in future conflicts.