University of California, Irvine (UCI) researchers conducted a thorough examination of peer-reviewed literature on the most prevalent mental health disorders and found that circadian rhythm disruption (CRD) is present in nearly all of them. However, correlation is not causation, so it is not clear if the mental disorders cause circadian disruption, if circadian disruption causes mental disorders or both in a positive feedback loop.

Pierre Baldi, UCI Distinguished Professor of computer science, and Amal Alachkar, neuroscientist and professor of teaching in UCI’s Department of Pharmaceutical Sciences.

The most common mental disorders were found to correlate with circadian disruption, including: anxiety, autism, schizophrenia, Tourette syndrome, ADHD, bipolar disorder, obsessive-compulsive disorder (OCD), anorexia nervosa, bulimia nervosa, food addiction, and Parkinson’s disease.

Circadian rhythms are intrinsically sensitive to light/dark cues, so they can be easily disrupted by light exposure at night, and the level of disruption appears to be gender-dependent and changes with age. One example is a hormonal response to CRD felt by pregnant women; both the mother and the fetus can experience clinical effects from CRD and chronic stress.

The researchers explored the interplay of circadian rhythms and mental disorders with gender. For instance, Tourette syndrome is present primarily in males, and Alzheimer’s disease is more common in females by a ratio of roughly two-to-one.

Age also is an important factor, according to scientists, as CRD can affect neurodevelopment in early life in addition to leading to the onset of aging-related mental disorders among the elderly.

To address causal attribution, the UCI-led team suggests an examination of CRD at the molecular level using transcriptomic (gene expression) and metabolomic technologies in mouse models. The researchers believe that if the experiments were conducted in a systematic way with respect to age, gender, and brain areas to investigate circadian molecular rhythmicity before and during disease progression, it would help the mental health research community identify potential biomarkers, causal relationships, and novel therapeutic targets and avenues.

This project involved scientists from UCI’s Department of Pharmaceutical Sciences, Center for the Neurobiology of Learning and Memory, Department of Computer Science, Department of Neurobiology and Behavior, and Institute for Genomics and Bioinformatics; as well as UCLA’s Oppenheimer Center for Neurobiology of Stress and Resilience and Goodman-Luskin Microbiome Center. The National Institutes of Health provided financial support.

You can read the full article published in the Nature journal Translational Psychiatry, here.