Researchers at the Brookhaven National Laboratory in New York have found that drug addicts with a low level of the genotype called MAOA (monoamine oxidase A) also have lower gray matter density - and therefore fewer neuron density - in regions of the brain necessary for decision-making, self-control, learning, and memory. MAOA, an enzyme that regulates the release of serotonin and dopamine in the brain, is involved in the processes that control mood and behavior. Compared with those with a higher MAOA genotype, individuals with a low MAOA genotype are more susceptible to severe drug addiction.

In a volunteer-based study, a team of researchers led by Nelly Alia-Klein-a medical student recently honored at Brookhaven National Laboratory-analyzed the genotypes of 40 drug-addicted males and compared their results with 42 non-drug-addicted males. All 82 participants provided a DNA sample in order to determine whether they had a high or low MAOA genotype. Additionally, the participants underwent brain scans using magnetic resonance imaging as well as a process called voxel-based morphometry to help researchers measure the volume of gray matter in the entire brain. The researchers also considered the type of drug the substance-using volunteers abused, as well as the extent of their abuse. Their study has been published in a recent issue of the scientific journal Archives of General Psychiatry.

In their results, the researchers learned that - similar to previous studies involving cocaine-dependent individuals - the drug-addicted participants had lower gray matter density in the frontal region of brain (where judgment and emotions are controlled) and the hippocampus (where learning and memory are stored) than those participants from the non-drug-abusing group. Specifically, the current study’s findings showed that drug-abusing individuals with a low MAOA genotype had less gray matter volume than both the addicted individuals who had a high MAOA genotype and the non-drug abusing participants. Furthermore, the presence of low gray matter was also correlated to one’s extent of their drug use and the type of drug abused, including alcohol, cocaine, and nicotine. The longer the participant had been abusing the substance, the lower their gray matter volume had become.

The findings indicate that drug addicts with a low MAOA genotype may require a specialized type of treatment in relation to those patients with higher MAOA genotypes. Although further research is needed in order to determine what types of changes to drug addiction treatment strategies need to be made, the researchers suggest that their findings significantly add to the development of more effective addiction treatment on a neurobiological level. In the future, the researchers also recommend studying whether the same findings are prevalent among female patients since the current study did not involve women subjects.

Not only could drug treatment help prevent addicted individuals from causing more damage to these important brain regions, but they may also gain better control over their executive function and learning, and therefore have a greater chance of recovery and abstinence. The researchers claim that their findings could help clinicians and other professionals to help addicted individuals receive the right type of treatment by considering both their genetic influences and their long-term drug abuse.

Source: HealthDay, Genes May Affect Severity of Drug Addiction, March 8, 2011