People who’ve recently used crystal methamphetamine at least once a week may be nearly four times as likely to develop non-Hodgkin’s lymphoma (NHL)—a cancer of the immune system—as people who use it less frequently or not at all, according to a study published in the July issue of Cancer Causes & Control.

Though NHL is diagnosed less frequently now than in the days before combination antiretroviral therapy, it remains a significant cause of death among HIV-positive people. Given that the cancer targets disease-fighting white blood cells, anything that perturbs the immune system could theoretically increase the risk of developing NHL. A number of laboratory studies have documented that crystal use can significantly affect the immune system, but few have shown what kind of clinical impact it may have.

To see whether there’s a possible link between using crystal meth and developing NHL, Chun Chao, PhD, from the department of research and evaluation at Kaiser Permanente Southern California in Pasadena, and her colleagues examined medical records and behavioral surveys from HIV-positive men enrolled in the Multicenter AIDS Cohort Study (MACS) collected between 1984 and 2002. During the course of the study period, 171 cases of NHL were diagnosed.

After adjusting for factors such as demographics and other drug use, Chao’s team found that frequent crystal use was strongly associated with lymphoma risk. They first looked at people currently reporting weekly crystal use and found that they were nearly 373 percent more likely to develop NHL. People who used crystal frequently at any time in the past three years were 205 percent more likely to develop NHL, compared with those without a history of frequent use. People who’d used crystal frequently more than three years ago—and were no longer using the illicit drug—were 75 percent more likely to develop NHL.

As this is the first study to find an association between crystal and NHL, the authors are encouraging further research to confirm their findings.