A University of Central Florida study has found that a gene variant, thought to be carried by nearly 25 percent of the population, increases the odds of developing depression.

People with apolipoprotein-E4, called ApoE4 for short, have a 20 percent greater chance of developing clinically significant depressive symptoms later in life compared to those who don’t have the gene variant, said Rosanna Scott, lead author of the study published in The Journal of Clinical Psychiatry. She will present her work at the International Association of Gerontology and Geriatrics conference in San Francisco. Scott, a Ph.D. candidate in clinical psychology, found the link while working on her thesis.

“Some genes are deterministic, like the one that causes Huntington’s disease — where if you’ve got it, you’ll get the disease. This isn’t one of those genes,” said Daniel Paulson, Scott’s faculty advisor and an assistant professor of psychology who co-authored the study.

Scott used health and well-being data of 3,203 participants as they aged from 53 to 71 years old. The data came from the Wisconsin Longitudinal Study, a long-term study of health, relationships, mortality and more of people who graduated from Wisconsin high schools in 1957. Those who have ApoE4 reported more symptoms of depression as they aged.

“Her thesis addressed a critical gap in the theoretical framework of this area of study,” Paulson said. “Now we can more systematically move forward with research on causes and treatments for late-life depression.”

Scott wanted to study ApoE4 and its potential links to depression because this variant of the ApoE gene is also known to negatively impact how a body handles cholesterol. Previous research — and Scott confirmed in the first paper of her thesis published in the International Journal of Geriatric Psychiatry — found that vascular-system risk factors such as high cholesterol, hypertension and high blood sugar also increase risk for depression. Vascular burden impacts how blood and nutrients are delivered throughout the body and to the brain, therefore impacting mood. Scott wondered if adults with ApoE4 and high vascular burden are at a compounded risk for depression.

Her research concluded that ApoE4 and poor vascular health do not create a compounded risk, but both independently increase the likelihood of depression.

Scott’s findings add clarity to the literature that’s already out in the scientific community on this topic, Paulson said. Prior research findings were inconsistent regarding ApoE4 and its risks for depression, and were done with small sample groups, too young a sample, or with data that wasn’t collected during a long period of time, she said.

Scott aspires to specialize in neuropsychology after completing her Ph.D. She’d like to work in academia to help guide student researchers like herself, and she’d also like to provide neuropsychological assessment and therapy services to the community. She’s particularly interested in chronic health conditions and how they impact mood in older adults.

“Bottom line, you do statistically have a higher risk of developing depression if you have ApoE4, but it’s not deterministic. You can’t change your genes, but you do have some control over improving your health,” she said. “That should be encouraging.”

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