The scientists first examined measures of executive function, the ability to perform complex tasks such as planning or decision-making that require attentional focus, and then imaged the white matter of the brain. They found that the integrity of the white matter and stable executive function appear to be important for maintaining healthy mood states in late life.
Research participants included 716 community-dwelling adults who were assessed to have normal cognitive and neurological function. Mood was measured using the Geriatric Depression Scale (GDS). The neuropsychological assessment included tests of executive function, memory, and processing speed (the time it takes to comprehend information and respond). A subset of 327 participants also underwent brain magnetic resonance imaging (MRI) within six months of completing the GDS and neuropsychological assessments.
The investigators found that mood improved with increasing age until around the early 70s, at which point the positive effect of age on mood plateaued, and eventually reversed. Stable white matter integrity, along with stable executive function and processing speed, appeared to protect against this reversal of positive mood.
Because the study was observational, these findings cannot be interpreted to show causation. Further research is needed to determine whether the brain-mood relationships are bidirectional. Another caveat is that the participants were mostly white and highly educated. Observed relationships between mood, age, white matter integrity, and cognition need to be evaluated in racially and educationally diverse groups. The researchers also suggest that future studies of the links between brain health, cognition, and mood should be large-scale, longitudinal, and use methods to allow capture of the full range of neurodevelopment. Results of such studies could inform interventions across a variety of neurodegenerative and neuropsychiatric conditions.