A Perth-based researcher has called for an end to the stigma surrounding marriage between cousins, after uncovering evidence that the health risks have been greatly exaggerated.



Murdoch University adjunct professor Alan Bittles has shed new light on the consequences of intra-familial marriages, which he says are on the rise in Australia due to increased migration.



Bittles has sought to address common misconceptions of same-blood marriage, from a social, medical and religious perspective, in a new book based on 35 years of research.



Bittles claims more than 1.1 billion people are either married to a close relative or are the offspring of such a marriage, which are common in many Muslim, Buddhist, Christian, Hindu and Jewish communities.



In his book, Consanguinity in Context, Bittles called for greater understanding and acceptance of the practice, which is largely taboo in Western countries.



He said there was a general belief that first cousin marriages lead to negative genetic outcomes, yet a large majority of children born to first cousins are healthy.



And in many cases of those born with defects, non-genetic factors were often to blame.



Bittles said many of the countries in which first or second cousin marriage was common were afflicted with poverty, which could have a devastating effect on health and development.



"Our findings over years of research have shown that the health risks associated with consanguineous marriage have been exaggerated, largely due to flawed research design, with a failure to allow for non-genetic factors that can adversely influence health outcomes," he said.



His research found that early death or major ill-health was on average four to five per cent higher in children of first cousins than other offspring.



Bittles said there could be some genetic advantages to same-blood offspring.



"But mainly the advantages are social and economic in nature, with the strengthening of family ties, and the maintenance of family goods, including land-holdings," he said.



He hoped his work would be the catalyst for more research into the outcomes of intra-familial marriages particularly the health effects on offspring as they enter adulthood.



"The central aim in my work is the prevention of genetic disease through a better understanding and appreciation of how genes are transmitted within families and communities," he said.