Late-onset depression, which first emerges in people aged 60 and over, is linked to a decline in the brain's executive functions that leads to repetitive, negative thought patterns a new study reveals. Executive functions are those that enable people to plan and control their thoughts and actions.
Published in the current issue of Cognitive Therapy and Research, the finding is based on a survey of 44 people suffering from depressive symptoms. Aged 66–92 years, the study's participants came from retirement communities in Sydney, Australia. The study's lead author, Bill von Hippel, says evidence for the conclusion is based on three findings.
"First, the people with late-onset depressive symptoms showed poorer performance on executive function tests than those with early onset depression." "Executive decline" is a normal part of ageing linked to decreased efficiency in the brain's frontal lobes. Typical signs of executive decline include disinhibition, rigid thinking, inattention and a decline in working memory.
"Second, we saw that executive decline was associated with rumination – a tendency for repeated negative thinking patterns -- among those with late-onset depression," says von Hippel, who is associate professor of psychology at the University of New South Wales. "We saw no such link among those who had early-onset depression."
"Third, the link between executive decline and late onset depression was brought about by their joint association with rumination. That is, executive decline was only associated with late-onset depression to the degree that it led people to ruminate. When executive dysfunction did not lead to rumination, it did not predict late-onset depression.
"Clinical rumination is like problem-solving gone awry – it's a wrong turn," says Dr von Hippel. "Looking inward and being reflective is a useful thing to do, especially when negative events happen in our life. But if we get stuck in a pattern of saying 'why me?' there's a risk that we can spiral into a pathology. Instead of solving the problem we just stew in it."
Dr von Hippel says longitudinal research is now necessary to reveal whether executive decline causes excessive rumination and late-onset depression, or whether some other related process underlies these associations. "By measuring mental functioning before and after late-onset depression develops, we'll get a clearer idea of the role of executive dysfunction in the development of excessive rumination and late onset depression. We also hope to get a clearer idea of when executive dysfunction leads to rumination and when it does not."
"What we can say is this," he adds. "Executive decline is a normal part of ageing, but late-onset depression is not. Feeling sorrow after negative events is also normal, but excessive rumination is not. Our current research suggests that for some people, these normal processes spiral out of control. Our goal now is to get a clearer idea of when and why executive dysfunction leads to these pathological outcomes, and what we might do to circumvent this process."
Materials provided by University of New South Wales. Note: Content may be edited for style and length.
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