A brain enzyme known to be involved in mood disorders may be in short supply in the brains of teenage suicide victims, a finding that could point to possible drug therapy, researchers said on Monday.

Whether the lack of the enzyme, protein kinase C (PKC), was a cause or an effect of the mental state that led to suicide was not clear from the post-mortem study of the brains of 34 teenagers, half of whom had committed suicide and the rest who died from other causes.

The researchers said the lower levels of the enzyme may be related to abnormalities in the interactions between the brain and hormonal glands. The enzyme is targeted by some mood-stabilizing drugs.

Whatever the mechanism, the decreased level of the enzyme is a “vitally important observation that will help not only in understanding the neurobiological profile of teen suicide but also in advancing ideas for therapeutic intervention,” said study author Ghanshyam Pandey of the University of Illinois at Chicago.

Thirty thousand Americans die of suicide annually and it is the second-leading cause of death among U.S. teenagers.

The suicide rate has risen sharply among male teenagers in the past two decades, said the study, published in the July issue of The Archives of General Psychiatry.