Runs in the family
What role do your genes play in predisposing you to becoming addicted?
Sometimes the chances of addiction are strongly influenced by a person’s genetic make-up. The most-used method of studying this is to compare the lives of pairs of identical twins (who share the same variations in DNA sequence) and non-identical pairs.
Traits that show a closer resemblance in the identical pairs are typically under stronger genetic influence. On this basis, there are genetic factors involved in susceptibility to alcoholism, and in the use of other drugs such as cocaine, heroin and nicotine. We can inherit different versions of certain genes that produce variation in the ways particular substances such as nicotine are processed (metabolised) in cells. Genes can alter levels of one of the chemicals that act as neurotransmitters, helping brain cells to signal to each other. Finally, there are genes that influence general aspects of behaviour, such as risk-taking or a desire for new experiences.
For instance, smokers who have one version of a gene for a dopamine-regulating enzyme have problems concentrating when they are low on nicotine, and find it harder to give it up. Additionally, people classified psychologically as novelty-seekers are likely to have fewer of a particular type of dopamine receptor.
The inherited influences on anyone’s vulnerability to addiction are normally a result of complex combinations of such genes, working out in ways that are affected by the person’s life and environment. This is explained in the diathesis-stress model, which states that it is a combination of biological factors and environmental factors that can lead to addiction. Diathesis relates to an individual’s vulnerability to an addiction, usually encompassing biological factors – including their body’s biochemical response to substances or their behavioural patterns and impulsiveness. Stress relates to environmental factors that can trigger an addiction. For example, a person may be biologically more predisposed to developing an addiction, but if they never encounter a trigger, they may never actually develop an addiction.
Another factor that has been shown to be involved in addiction is age-related brain development. The concept of a ‘teenage brain’ is still controversial, but brain-imaging techniques have shown that brain development might be linked with impulsive behaviour, which may be why teens are more likely to try alcohol, tobacco or drugs. The amygdala, a brain region involved in emotion, fear and aggression, develops early on, but the frontal cortex, involved in judgement and reasoning, doesn’t fully develop until the age of 25. This means the teenage brain is more likely to be ruled by the amygdala than the prefrontal cortex, leading to impulsive behaviours and risk-taking.Lead image:
Peter Voerman/Flickr CC BY NC