Co-scientist Ming Li of Virginia University said: "We have found several genes are linked with multiple addictions.

So, we are narrowing the scope to specific genetic targets.

"Once researchers can pinpoint exact genetic variants and molecular mechanisms, then we can create more effective, even personalised, treatments for individuals addicted to a variety of substances."

In their study, the scientists have revealed a summary of specific genomic locations on 11 chromosomes where addictions to alcohol, cannabis, cocaine, heroin, nicotine and opoids are clustered together.

"The comparison of peaks for addictions to multiple substances on certain chromosomal locations confirms genetic vulnerability to different substances overlaps, in part," Li was quoted by the media as saying.

The scientists have further pointed out that variants in several genes, including aldehyde dehydrogenases, GABRA2, ANKK1, and neurexins 1 and 3, have already been associated with addictions to multiple drugs.

And, in recommending a future direction for research into the genetics of addiction, they suggested focusing on the CHRNA5, CHRNA3 and CHRNB4 clusters, among other variants.

"The exact nature of the gene variants and how they function are still unknown, so functional studies as well as studies using additional ethnic population samples may be quite revealing," Li said.