Here's another one to add to the list of Weird Studies and one bright side to being a nerd in high school. Having sex as a teenager could have a lasting effect on your brain and lead to depression in the future. Well, at least if you're a male hamster. A study conducted by researchers at Ohio State University found that hamsters that had sex when they were 40 days old (the equivalent to being a teenager in humans) were more likely to show signs of depression as adults. To conduct the study, they had one group of male hamsters mate when they were 40 days old (hamsters reach puberty at 21 days). A second group mated when they were 80 days old, while a third wasn't exposed to female hamsters at all.
At 120 days, the hamsters were given tests to gauge their mood. The teen sex hamsters were more likely to stop swimming when placed in a shallow pool, a sign of depression. All the hamsters that had sex also showed signs of anxiety by refusing to explore a maze as opposed to the virgin hamsters. Their brains were hard-wired differently as well. The sexually active hamsters had less complex brain dendrites—the neuron branches that receive signals. "We think that pubertal testosterone organizes neural circuits during adolescence in a way that maximizes male-typical social responses and behaviors in adulthood," explained Cheryl Sisk, whose initial research about adolescent sex in rodents prompted the OSU study. In other words, early sex, which increases testosterone, actually reorganizes the way the male brain functions, leading to long-term changes in how men think as adults. One benefit they found, however, was that the males who had sex were leaner and had stronger immune systems. The research is still in its preliminary stages, and they haven't been able to say definitively if this applies to humans as well, but there have been other studies linking teen sex in humans to depression. "There is previous evidence that the age of first sexual experiences correlates with mental health issues in humans," Zachary Weil, a research assistant professor of neuroscience at Ohio State, explained to LiveScience. "But with all human research, there are a number of other variables involved, such as parental supervision and socioeconomic status, that may be involved with both the age of first experience and depression."