Risk factors for dementia are not associated with cognitive dysfunction in young people with major depressive disorder

Abstract Background : Hippocampal thinning and carrying the e4 allele of the apolipoprotein E (APOE) are associated with reduced cognitive performance in older people. Although cognitive impairment is also frequent during and after depressive episodes, it may occur irrespective of age, which makes it difficult to determine, whether this symptom indicates a risk for or shared mechanisms with neurodegeneration. We therefore investigated the influence of genetic and brain imaging risk factors for dementia on cognitive impairment in young people with major depressive disorder. Methods We used magnetic resonance imaging, APOE genotyping and neurocognitive assessments to examine young adults (mean age: 29.1 ± 6.3 years) with major depressive disorder and a current depressive episode, presenting with or without cognitive deficits. Results Neither hippocampal thickness nor APOE genotype predicted cognitive impairment. Patients with objective cognitive deficits reported a greater number of previous depressive episodes. Limitations Our results have to be interpreted with caution. The small sample size could have prevented the detection of effects. Complementing research methods and investigations across the life span would be necessary to reveal possible interactions between risk factors for dementia, neurodegeneration, depression, and age. Conclusions In young adults, recurrent depressive episodes may increase the likelihood for cognitive deficits, while common risk factors for dementia do not.