A new study by a team of researchers in the Behavioral and Clinical Neuroscience Institute may help explain why regular cocaine users are more likely to contract an infectious disease than those with no history of drug addiction. The research was recently published in the journalBiological Psychiatry.
The researchers found that cocaine-dependent men have heightened physical and biological ‘warning’ reactions to visual clues that convey risk of infection, such as rotten food and dirty toilets. These oversensitive bodily reactions may be borne from a history of recurrent infection. Yet their lack of awareness about their bodies alarm signals could cause cocaine users to not protect themselves adequately, putting themselves at greater risk of contracting an infectious disease.
Infectious diseases are the most common and costly health complications of drug addiction and chronic drug users are particularly high risk of contracting infections such as HIV, hepatitis B and C, even if they are not injecting drugs. Rates of other infections such as tuberculosis and sexually transmitted diseases are also high amongst people who regularly consume addictive drugs such as cocaine.
Until now it has widely been believed that cocaine users’ high infection rate is due to their tendency to engage in ‘risky behaviours’, such as unprotected sex, or sharing pipes and straws, which exposes them to disease-causing pathogens. It has also been suggested that cocaine itself might interfere with the body’s immune response to infectious agents, like viruses and bacteria, leaving drug users more vulnerable to infection.
The researchers studied 61 men, 31 of whom were cocaine-dependent, and showed them a series of neutral and ‘disgusting’ pictures, which were not related to drug taking but depicted general scenes related to dirt, decay, wounds and excrement. They recorded their physical and behavioural response to the pictures by measuring levels of immunity (cytokines) in their saliva and using techniques similar to lie detector polygraph to test their unconscious reaction to the pictures. They also asked the men about their personal hygiene habits, for example how often they washed their hands.
The cocaine-addicted group had higher levels of immune chemicals and more pronounced unconscious reactions in response to the disgusting images then the control group. This type of ‘hypersensitivity’ reaction is typical of people who are prone to repeat infections and is due to a type of Pavlovian-type conditioning, where the immune system ‘learns’ to associate unhygienic surroundings with impending illness and, as a result, prepares to fight infection.
Dr Karen Ersche, who led the research, said ”our study clearly shows that cocaine users have abnormal responses to situations that might, in the real world, present an infection risk. Although their bodies were highly sensitive to the disgusting pictures, the cocaine users themselves seemed unaware of their heightened risk, which may explain why they are not taking special care in protecting themselves and are reluctant to make use of preventative measures on offer for them. These findings bring to light two key points, namely that regular cocaine users need to be made aware of their increased risk for infectious diseases, and researchers need to find out how the immune system in regular cocaine users has changed in order to develop treatments to reduce the risk of infections in these people. There are also wider implications for policies that aim to reduce the harmful consequences of drug use.”
The researchers are now planning a new study to learn more about the effects of cocaine on the immune system, specifically in the blood, which they did not look at in this study. They also aim to explore new avenues of making harm reduction interventions more effective in chronic cocaine users.
The research was funded by the Medical Research Council. This news post was adapted from the Medical Research Council press release.