A recent article in the Sydney Morning Herald found that around 50 per cent of the risk of drug or alcohol dependence abuse is genetic.
Although there's no single addiction gene, there's a cluster of inheritable traits that can make some people more vulnerable, says geneticist Dr Margaret Smith.
"It helps explain why some people can experiment with drugs and move on while others become dependent," says Smith, the author of Gene Genius, a new book on the influence of genes on our health and wellbeing.
So what are these genes that can nudge us towards dependence?
The novelty seeking gene
Some of us are born with a novelty seeking version of a gene called DRD 4 that can colour our lives in different ways – it can be part of why some people are drawn to base jumping or sky diving but it's also linked to opiate dependence, smoking, alcohol use and risky behaviour, Smith explains. The thing about this gene is that it has different effects depending on which version you have - the long one, the short one or the middle-size one. It's the long one that can steer you towards sensation seeking, while the short one puts you at the other of the risk taking spectrum – content with a jog rather than free-climbing a cliff face.
Genes that influence our levels of the 'happy chemical' dopamine
Genes can also influence how much dopamine our brains produce, she adds. Some people, including those with the long version of DRD 4 or other types of dopamine gene receptors such as DRD 2, tend to have lower levels of dopamine that make them more vulnerable to substances like drugs that raise dopamine levels, making them want to come back for more.
A family history of anxiety and depression
Anxiety and depression can both raise the risk of alcohol or drug dependence – and genes can also contribute to anxiety and depression, Smith says.
"Recent studies have reported as much as 40 percent of those with depression can trace it to a genetic link. Environmental and other factors make up the other 60 percent."Understanding the part genes play challenges our notions of the causes of drug and alcohol dependence – that it's all down to some character flaw or because we're poor and disadvantaged. Drug or alcohol dependence can happen to highly educated recreational users. We live in a high pressure environment and people want a quick release."Just like type 2 diabetes, substance abuse can result from a combination of our genetic inheritance and our environment – but we don't beat people up because they develop diabetes."
Having a parent with drug or alcohol dependence can increase your own risk although it may not be through genes alone – the way in which drugs or alcohol are used in the family and the impact on the quality of family life can also contribute, says Professor Steve Allsop, director of Curtin University's National Drug Research Institute.
"We should always treat alcohol with respect, but if a parent has a severe problem with alcohol you should treat it with even more respect and avoid letting alcohol become a central part of your life – don't drink every day, for example," he says. "Just because there's a family history of alcohol doesn't mean this is your destiny. But you need to think about how you use alcohol and ask yourself, 'Do I drink above the guidelines for low risk drinking?"
"How do I use alcohol – is it because I like the taste or enjoy a drink with a meal or in company or am I just drinking for the effects?"
The important thing is not to be in denial about a family history of substance abuse – we should talk about it to our kids just as we would with a family history of breast cancer or melanoma, says Professor Ian Hickie, co-director of health and policy at the University of Sydney's Brain and Mind Centre.
"When it comes to managing our personal health we all need to have a better understanding of what the individual risks to our health are and how to reduce them – and families can't afford to be blind to the risks of a family history of substance abuse."