University of Otago researchers said the odds were even greater for young women, Stuff.co.nz reported.
The more sex partners young women have, the more likely they are to become dependent on drugs and alcohol, they said.
As part of the study the researchers tracked the health and behaviour of more than 1000 people from birth in Dunedin in 1972-73. They looked at how many sex partners the study participants had during three age periods: 18-20, 21-25, and 26-31 years.
Dr Sandhya Ramrakha, the study’s lead author, said women who had 2.5 or more partners each year increased their odds of having a substance dependence disorder by up to 17 times.
Further, when the researchers used a model to compare men and women who had more than 10-20 sex partners in the same periods, they found that these women were much more likely to have a substance disorder than the men.
The strong link between the number of sex partners and substance disorders stayed even after taking into account pre-existing mental disorders and substance problems, said Dr Ramrakha.
The researchers believe the reason behind it could be that sex, drugs, and alcohol were part of a cluster of “risk-taking behaviours” that developed in adolescence.
“Or it may be due to the disinhibitory effects of alcohol and cannabis providing opportunities for sexual behaviour,” said Ramrakha.
Context may be another explanation, that is, pubs and bars are also places where one can easily meet partners, she added.
Ramrakha has expressed the need for more research to figure out what was exactly behind the link so solutions could be found.