London, July 2 (IANS): It can be predicted if young adults are prone to developing problem drinking or engage in risky sexual behaviour in response to stress, says a new study.

"By knowing the biology that predicts risk, we hope to eventually change the biology -- or at least meet that biology with other forces to stem the risk," said the senior author Ahmad Hariri, professor of psychology and neuroscience at Duke University.

The team used non-invasive functional Magnetic Resonance Imaging (MRI) imaging to measure the activity of two brain areas that help shape opposing behaviours crucial for survival.

These include: the reward-seeking ventral striatum and the threat-assessing amygdala. Having both an overactive ventral striatum and an under-active amygdala was associated with problem drinking in response to stress.

The inverse brain pattern predicted problem drinking in response to stress both at the time of the scan and three months after. Interestingly, people with the two different risk profiles may drink for different reasons.

Balance in the activity of the ventral striatum and the amygdala also predicts sexual behaviour.

The team asked 70 heterosexual men and women how many new sexual partners they acquired over an 11-month period.

For men, the same pattern of brain activity linked to problem drinking -- high ventral striatum and low amygdala activity -- was associated with a greater number of sexual partners compared to those men with more balanced activity of the two brain areas.

But the pattern for more sexually active women was different.

They had higher-than-normal activity in both the ventral striatum and the amygdala -- indicating both high reward and high threat.

The results were outlined in the journal Molecular Psychiatry.