Image Credit: Stas Knop, Pexels (CC0)
Our bodies are regulated by an internal circadian clock that aligns physiological processes to a 24-hour day-to-night cycle. However, the timing of this rhythm can vary: some people are ‘early birds’ who prefer mornings, while others are ‘night owls’ who prefer to wake up and stay up late.
Circadian rhythms have been closely linked to neuropsychiatric conditions like depression, as well as specific psychiatric symptoms such as reduced motivation. Despite this, the circadian clock is seldom considered when investigating the cognitive and motivational changes associated with mental health conditions.
To address this gap, Mehrhof and Nord designed a study to assess motivational differences in the general population and examine whether there were associations between neuropsychiatric symptoms and circadian rhythms. The study focused on effort-based decisions – where individuals choose whether completing a task is worth the effort of the reward – as disruptions in this process often underpin motivational deficits in neuropsychiatric disorders.
Mehrhof and Nord found that individuals with high neuropsychiatric symptoms were less likely to undertake effort-based tasks, consistent with previous studies. Night owls showed the same motivational deficit – even when taking into account neuropsychiatric differences. However, this loss of motivation only occurred when the night owls were tested in the morning. When tested in the evening, their performance matched that of individuals who had an earlier circadian rhythm.
These findings suggest that the circadian clock and neuropsychiatric conditions affect motivation in independent but parallel manners. In addition, testing someone at times of day that misalign with their circadian rhythm may be skewing the results of psychiatric studies. Further research could explore whether aligning treatment schedules and daily routines to a person’s internal clock improves motivation and other mental health outcomes.
