WELLINGTON, Dec. 5 -- Low levels of the naturally occurring mood-altering brain chemical, serotonin, can make some people more likely to become drug addicts, according to New Zealand research released on Friday.

The finding could lead to the development of drugs that prevent drug addiction, Victoria University psychology researcher Sarah Bradbury said in a statement.

Her study found that levels of serotonin, the chemical responsible for maintaining mood balance, during initial drug use were critical to whether someone becomes drug dependent or not.

"The higher the serotonin levels someone has, the less likely they will become addicted," she said.

Once drug use escalated and became frequent, the anti-addiction effect of serotonin decreased.

"Another brain chemical, dopamine, seems to be the critical determinant of drug addiction during this phase," she said.

Addiction research was increasingly investigating a variety of brain chemicals in a bid to further understanding of the disease, and with the aim of producing pharmaceutical therapies to help prevent and treat drug addiction.

Bradbury said her results suggested that therapies that increase serotonin levels could be investigated as a way of preventing drug addiction.