Hit me, it turns out, is contagious. A new study conducted by University of Iowa researchers has found that pathological gambling and the gambling addiction that often follows tends to run in people’s families.

Most troubling about pathological gambling is that it doesn’t happen in a vacuum. Swirling around it is a complex mix of social anxiety disorders, post-traumatic stress disorder (PTSD), major depression, and typically substance abuse. The latest findings confirm this whirlwind’s presence, and also solidify pathological gambling as very much a familial disorder: If one family member has a problem, a relative nearby is eight times more likely to develop one, too.

"People have always thought pathological gambling ran in families — anecdotal evidence certainly suggested it. But when you finally do a study like this, which is the largest of its kind, and come up with figures like this, it is quite striking,” said lead author and professor of psychiatry in the UI Carver College of Medicine, Dr. Donald Black, in a statement.

Black and his colleagues defined pathological gambling as chronic gambling so serious it may become a clinical issue. More than a loose “gambling problem,” pathological gambling sees people succumbing to gambling compulsions. Their lives revolve around gambling and the thrill they seek from it.

To understand its contagiousness, the team collected data on 95 pathological gamblers and 91 control subjects, matched for age, sex, and level of education, along with 1,075 first-degree adult relatives of the study participants. First-degree relatives include parents, siblings, and children. Overall, they found 11 percent of the gambling relatives were pathological gamblers, compared to only one percent of the control relatives. "Our work clearly shows that pathological gambling runs in families at a rate higher than for many other behavioral and psychiatric disorders," Black said.

The team then conducted a follow-up analysis to find out if problem gambling, which contained a larger pool of subjects, exhibited the same relationship. Less narrowly defined, they speculated that people who were problem gamblers would transfer that behavior to their relatives in greater proportion. What they found was that, where only three percent of the control group’s relatives had gambling problems, a staggering 16 percent of the experimental group’s relatives did.

Such a strong connection should give doctors concern, Black argues, not just for the patients they treat who have gambling problems themselves, but for their family members. The experimental results in their first analysis matched up well with the national average for pathological gambling — between 0.5 and one percent of the population, or more than 3.1 million people. However, this means that the first-degree relatives — more than 30 million people — are also at risk.

"I think clinicians and health care providers should be alerted to the fact that if they see a person with pathological gambling, that person is highly likely to have a close relative with similar or the same problem,” Black explained. “That is a teaching moment and they should probably encourage the patient to let their relatives know that help is available."

If they don’t, serious mental health obstacles could eventually crop up. Using statistical models to analyze diagnoses of depression, PTSD, and anxiety disorders, the team found an overabundance of these conditions in the relatives of pathological gamblers, irrespective of whether those relatives also had pathological gambling problems. This suggests certain disorders may share an underlying predisposition with pathological gambling, Black said.

Ultimately, the findings should give rise to advanced brain scans that can tease out what’s really going on neurologically. “Maybe this situation provides a better chance of finding genes that are linked to the gambling disorder,” Black said, “and maybe that would pave the way for improving our understanding of the genetic transmission in general for psychiatric disorders, particularly in the realm of addiction."

Source: Black D, Coryell W, Crowe R, et al. A direct, controlled, blind family study of DSM-IV pathological gambling. Journal of Clinical Psychiatry. 2014.