Experts believe the growing variety of antipsychotic drugs prescribed for the US combat forces impair the troops' ability to make correct judgments.

The United States Central Command allows troops struggling with sleep deprivation to receive a 6-month supply of Seroquel - a drug first developed to treat schizophrenia, bipolar disorders, mania and depression, according to a report published by AllGov on Sunday.

At least two US troops have died while asleep after having taken large amounts of the medication.

A June 2010 report released by the Defense Department's Pharmacoeconomic Center at Fort Sam Houston revealed that some 20% of the troops on active-duty are taking psychotropic drugs, ranging from antidepressants to antipsychotics to sedative hypnotics.

The consumption of these drugs by active troops can cause "loss of judgment and self-control and lead to increased violence and suicidal impulses" while on the field, experts say.

US troops have carried out acts of extreme violence on several occasions in Iraq and Afghanistan.

Last September at least twelve US soldiers were arrested for forming a secret "kill team" that shot and blew up civilians at random.

At least one of the soldiers collected the fingers of the victims as souvenirs and that some of them posed for photographs with the bodies.

Also in December Staff Sergeant Robert Stevens, 25, an Army medic from the State of Oregon, was sentenced to nine months in prison for killing Afghan civilians.

He confessed to opening fire on two Afghan farmers in March 2010 for no apparent reason.