Research has shown that people who use cocaine have an increased susceptibility to immune system problems, as well as increased risks for serious or life-threatening infections. Some of the immune system-related issues in cocaine users appear to come from secondary environmental factors; however, some of these issues stem directly from changes in normal immune function. In a study published in May 2014 in the journal Addiction Biology, researchers from Spain and the U.S. looked at the types of immune system disruptions that can appear in people addicted to cocaine. They also looked at the impact of immune system dysfunction on the severity of cocaine addiction. The Immune System The immune system is the network of organs, tissues and cells that helps defend the body from invading microorganisms and other non-infection-related sources of damage. Specific components of this system include a range of specialized cells that travel in the bloodstream, a group of widespread tissues and vessels known collectively as the lymphatic system, an organ in the abdomen called the spleen, an organ in the chest cavity called the thymus, the marrow found in the middle of the body\u2019s long bones and the skin. Each of these components works with the other to provide the coordinated responses necessary to deal with infectious agents and other sources of damage in a timely manner. Disruptions in one part of the immune system can have a cascade effect that branches out to other parts of the system. In some people, the immune system mistakenly attacks healthy organs or tissues instead of combating actual threats. Cocaine and Immune Function Cocaine users can place an undue burden on their immune systems by doing such things as sharing needles and displaying impaired judgment that leads to participation in unsafe sexual practices or certain other high-risk behaviors. However, the stimulant drug also has a harmful effect on organ systems throughout the body, including the respiratory system, the cardiovascular (heart and blood vessel) system and the central nervous system (brain and spinal cord). In addition, the drug has the ability to alter the health of several key components of the immune system. For example, in a study published in 2013 in the Journal of Leukocyte Biology, a team of U.S. researchers linked the use of cocaine to damaging changes in some of the key cells that act as a frontline defense against the human immunodeficiency virus (HIV) and other highly serious forms of infection. Impact on Cocaine-Related Problems In the study published in Addiction Biology, researchers from The Scripps Research Institute and 10 Spanish institutions used an examination of 82 people recovering from cocaine addiction to explore the immune system changes triggered by chronic exposure to the drug. They also examined the impact that increasing immune system dysfunction has on the severity of cocaine addiction, as well as on the odds that an addicted person will develop a mental illness such as an anxiety disorder, schizophrenia or some other psychosis-related condition, a mood disorder (depression or bipolar disorder) or a personality disorder. For the sake of comparison, a group of 65 people unaffected by cocaine addiction also took part in the study. The researchers concluded that a cocaine addict can experience as many as 11 damaging changes in key protein cells that help provide normal immune function. Some affected individuals only develop one or two of these changes, while others develop as many as nine or more. After comparing the number of immune system alterations present in an individual to the intensity of his or her cocaine addiction, the researchers also concluded that people heavily impacted by immune cell dysfunction (at least nine specific alterations) tend to have more severe addiction symptoms. In addition, they concluded that those cocaine-addicted individuals with highly compromised immune systems have clearly elevated risks for a co-occurring case of a personality disorder, anxiety disorder, schizophrenia\/psychotic disorder or a mood disorder. The particular level of risk elevation varies with the type of mental illness under consideration. In addition to their work with humans, the study\u2019s authors conducted experiments on mice that further confirmed the link between chronic cocaine use and certain critical changes in immune system function. They believe that their findings can potentially help doctors make more accurate assessments of people seeking treatment for cocaine-related problems, as well as making it easier to identify effective treatments.