Heroin Addiction and the MAOA Gene

by langm349 on April 6, 2017 - 11:39am

It seems like far too often I am hearing about friends or former classmates that have become addicted to heroin or have overdosed. It can be so frustrating sometimes, and you think to yourself why someone would do that, or why don’t they just stop. It is well known that addictions are extremely hard to overcome, but there may be another factor playing a part. An article published on March 27th, 2017 suggests that there is a connection between the low activity C allele of MAOA rs1137070 and a higher sensitivity to heroin addiction. It is also linked to the effects of heroin abuse on cognition function and the salience network. Approximately 40-60% of the development of addiction is based on genetics. The study discusses Monoamine oxidase A (MAOA), an x-linked gene that is associated with addiction, and other psychiatric disorders. MAOA activity has a significant role in the development of addiction, due to the fact that it controls amines like dopamine, histamine, and serotonin. At the 1460 location on the MAOA gene is the rs1137070 polymorphism. The study aims to discover the association between heroin addiction and MAOA rs1137070, it does this by measuring the distribution of the gene on a sample of healthy men and women controls and men and women heroin addicts. They then examine the effect of heroin addiction on gray matter volume (GMV) and neurocognitive skills. The C allele frequency at rs1137070 was found to be significantly higher in heroin addicts compared to the normal controls. In regards to gray matter volume, those abusing heroin with the C allele had lower GMV than those within the normal controls. A structural connectivity analysis was done, showing different structural connections between regions of the brain, for the control and the heroin abusers. The analysis also showed a weaker connection between the right insula and the temporal lobe, in heroin addicts. When tested on their neurocognitive performance, there were large amounts of gray matter deterioration or atrophy in those addicted to heroin, they also scored significantly higher on the Barratt Impulsiveness Scale, and scored much lower on the Montreal Cognitive Assessment and Iowa Gambling Task. These cognitive scores positively correlated with the measures of GMV in the orbital frontal cortex, and the right insula of the heroin addicts. Overall, the results of the study showed that there is an association between MAOA rs1137070 polymorphism and the addiction to heroin. Additionally, this addiction causes changes to gray matter volume in areas of the brain relating to cognitive function. It was also found that the C allele is connected to a proneness to heroin addiction.

Sun, Y., Liu, L., Feng, J., Yue, W., Lu, L., Fan, Y., & Shi, J. (2017). MAOA rs1137070 and heroin addiction interactively alter gray matter volume of the salience network. Scientific Reports, 7, 45321. doi:10.1038/srep45321

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Did the authors of this study make any suggestions about the possible reasons for the elevations they found in heroin addicts? How did they determine that the cognitive results were connected to the gene and not just the result of the heroin use?

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