There are clinical links between circadian rhythm disorders and mood disorders.
Disruption of circadian rhythms is related to behaviour and can be observed in various neurodegenerative diseases. When circadian rhythms and protein levels become disrupted, disorders can occur that are also related to dopamine imbalances, which explains why some disorders such as autism, Alzheimer’s, Parkinson’s and ADHD, in which dopamine is either deficient or imbalanced, are often accompanied by sleep, mood or alertness problems. For example, Parkinson’s disease causes a loss of dopaminergic neurons in the midbrain that produce dopamine.
Decreased dopamine levels in the retina impair adaptation to light, thereby disrupting circadian rhythms
In the retina, its release helps the body recognise changes between light and dark and transmit this information to the suprachiasmatic nuclei (SCN) in the hypothalamus, which act as the body’s ‘central clock’. If dopamine levels in the retina decrease, the eye’s ability to respond and adapt to light deteriorates, which can interfere with the transmission of light signals to the SCN. The result is a disruption of the internal biological clock that not only affects sleep and wakefulness, but also mood, cognitive performance and overall well-being.
