Traumatic brain injury, described as the signature wound of the Iraq war, may be less to blame for soldiers' symptoms than doctors once thought, contends a provocative military study that suggests post-traumatic stress and depression often play a role.

That would be good news because there are successful treatments for those conditions, said several nonmilitary doctors who praised the research.

Thousands of soldiers returning from Iraq have struggled with memory loss, irritability, trouble sleeping and other problems. Many have suffered mild blast-related concussions, but there is no easy way to separate which symptoms are due to physical damage and which are from mental problems caused by the traumatic stress of war. Imaging of the brain is being tested, but hasn't yet proven to be helpful.

People around the globe hit the height of their misery and depression in middle age, a new international study suggests.

The finding by British and American researchers was based on an analysis of well-being among approximately 2 million people in 80 nations. With few exceptions, the observation appears to apply across the board, regardless of gender, culture, geography, wealth, job history, education, and marriage or parental status.

"The scientific fact seems to be that happiness and positive mental health follow a giant 'U' shape through life," said study author Andrew J. Oswald, a professor of economics at Warwick University in Warwickshire, England. "For the average person, it's high when you're 20, and then it slowly falls and bottoms out in your 40s. But the good news is that your mental health picks up again, and eventually gets back to the high levels of our youth."

After decades of inattention to the possible psychiatric side effects of experimental medicines, the Food and Drug Administration is now requiring drug makers to study closely whether patients become suicidal during clinical trials.

The new rules represent one of the most profound changes of the past 16 years to regulations governing drug development. But since the F.D.A.’s oversight of experimental medicines is done in secret, the agency’s shift has not been announced publicly.

The drug industry, however, is keenly aware of the change. Makers of drugs to treat obesity, urinary incontinence, epilepsy, smoking cessation, depression and many other conditions are being asked for the first time by the drug agency to put a comprehensive suicide assessment into their clinical trials.

Genetic variations that predict patient response to the two common antidepressant drugs citalopram (brand name Celexa) and venlafaxine (Effexor) have been identified by German researchers.

The team at the Max Planck Institute of Psychiatry in Munich found that 11 variants in the gene for a protective transporter protein called P-gp, which removes drugs and other substances from the brain, compromise the effectiveness of these two drugs.

In the first part of the study, the researchers knocked out genes for P-gp in mice and gave them antidepressants. They found that brain concentrations of citalopram and venlafaxine were regulated by P-gp, indicating that the antidepressants were "substrates" of the transporter protein.