One reason the researchers from the Ohio State University College of Medicines believe could be that during adolescence the nervous system is still in the developing phase that can have broad consequences.
The researchers, who carried out their study on hamsters, found that the animals that mated earlier in life had higher levels of depressive behaviours, changes to the brain and smaller reproductive tissues compared to those that had intercourse later or not at all.
“Having a sexual experience during this time point, early in life, is not without consequence,” study co-author John Morris, a doctoral student in psychology at Ohio State, was quoted as saying by LiveScience.
However, the researchers cautioned that the study should not be used to promote teenage abstinence, as they noted that the research was carried out on hamsters and it isn’t certain the same conclusion will hold for humans.
As such, more research is needed understand the effects of sex during puberty, said the researchers who presented their study at the Society for Neuroscience annual meeting.
For their study, the researchers had a group of 40-day-old male hamsters (the equivalent of human teens) mate with adult females in heat. A second group of males mated in adulthood (80 days into life), while a control group was not exposed to females.
Hamsters reach puberty at 21 days, and by 40 days have reached late- to post-adolescence, roughly equivalent to ages 16 to 20 in humans, said lead study researcher Randy Nelson, a neuroscience professor and chair at Ohio State.
The researchers found that the animals that had sex at 40 days when placed in water were more likely to stop swimming vigorously, a symptom of depression, than the other three groups.
All of the sexually active hamsters showed higher levels of anxiety, measured by willingness to explore a maze, than the virgin hamsters.
The group that had sex in adolescence also showed less complexity in the brain’s dendrites, the branching extensions of neurons that receive messages from other nerve cells, and higher expression of a gene associated with inflammation.
Certain reproductive tissues, including the seminal vesicles (glands in males that secrete ejaculate) and vas deferens (tube that carries sperm out of the testes), were also found to be smaller in these animals.
However, the 40-day group also showed some benefits of early life sexual experience, the researchers said, including reduced body mass and enhanced immune responses in adulthood.
Although his team’s work may be useful in beginning to understand the physical and mental health outcomes of adolescent sex in humans, co-author Zachary Weil, a research assistant professor of neuroscience at Ohio State, said.
The key finding of the study is that experience during adolescence, when the brain is still developing, can have long-term effects on health and behaviour, he added.