Nova Scotia, Canada: Relatives of people with depression consistently performed less well on cognitive tests compared to people with no family history of mental illness, shows a new meta-analysis.
The study, published in the journal JAMA Psychiatry suggests that cognition may contribute to early identification of risk for depression and may be examined as a potential target for early intervention.
Barbara Pavlova, Nova Scotia Health Authority, Halifax, Nova Scotia, Canada, and colleagues conducted the study to compare cognitive performance between individuals with and without a family history of major depressive disorder (MDD).
This meta-analysis of 54 studies from 1980 to 2018 involved analysis of 8,468 individuals (3,246 first-degree relatives of people with major depressive disorder and 5,222 controls). Controls had no first-degree relatives diagnosed with MDD, bipolar disorder, or schizophrenia. The average age of relatives with MDD was 15.38 years and 57.68% were female; the average age of controls was 14.70 years and 55.93% were female.
For each cognitive test, the researchers computed the standardized mean differences (SMD) between the first-degree relatives of people with major depressive disorder and controls. Study characteristics were not significantly associated with between-group differences, and there was no evidence of publication bias.
- Across 284 measures of cognition in 54 nonoverlapping samples including 3246 relatives of people with MDD (mean age 15.38 years, 57.68% females) and 5222 controls (mean age 14.70 years, 55.93% females), relatives of people with MDD performed worse than controls across all measures of cognition (SMD = −0.19; 95% CI, −0.27 to −0.11; P < .001).
- Domain-specific meta-analyses showed a similar size of the relative-control difference in most domains of cognition, including:
- Full-Scale IQ: SMD −0.19
- Verbal intelligence: SMD −0.29
- Perceptual intelligence: SMD −0.23
- Memory: SMD −0.20
- Academic performance: SMD −0.40
- Language: SMD −0.29
This finding may mean that cognitive impairment is part of familial disposition to depression, Pavlova said. While it’s well established that people with major depressive disorder show cognitive impairment even in remission, it’s not clear whether the impairment is related to the illness or treatment, or part of a preexisting vulnerability, she noted.
“The distinction between the two alternatives matters: the former explanation would lead to search for different treatments, but the latter alternative informs causation and prevention,” Pavlova told MedPage Today.
“Looking at unaffected relatives is a good way of distinguishing between causes and consequences, but because relatives only share part of their genes, the size of the difference is smaller than in those who have depression themselves,” she added. “This is why it was necessary to bring together data from many studies to answer what may appear to be a simple question.”
There are several reasons why first-degree relatives of people with the major depressive disorder may have impaired cognitive performance, including genetic and social factors, Pavlova and colleagues noted.
It’s also possible cognitive impairment could result from subclinical depressive symptoms, or “parental depression could negatively affect cognitive development through environmental influences such as home environment or parenting style,” observed Jonathan Roiser, the University College London in England, and co-authors in an accompanying editorial.
For further reference follow the link: 10.1001/jamapsychiatry.2018.3672