Descartes’ mind-body dualism might sound antiquated, but it is still surprisingly prevalent within medicine. But, neuroscientist Camilla Nord argues, treating mental and physical health as separate domains is a mistake. Recent medical evidence shows that poor mental health and poor physical health often share a common underlying cause, highlighting the need for a fundamental shift in how we understand the connection between mental and physical health.

We all know that our bodily states can sometimes alter our mental experiences. Think to the last time you felt irritable, but later realised you were just hungry—or felt depressed the morning after a sleepless night. But for the most part, medicine still treats mental and physical health as though they were completely independent of one another. This mind-body dualism is not only misguided, but can be dangerous when informing the treatments doctors provide (or fail to provide) for mental and physical ailments alike.

Mental illness tragically shortens life expectancy by about 15 years for women and 20 years for men: this is called the ‘mortality gap’. Most of this mental health mortality gap is not driven by what one might think, thinks like self-harm, addictive substance use, or suicide. It is actually accounted for by physical health, particularly cardiometabolic health such as high blood pressure and Type 2 diabetes. Mental and physical health are closely intertwined by common risk factors and intersecting biological processes supporting mental and physical health. Increasingly, neuroscientific studies find physical origins, correlates, and consequences of mental health problems—and on the other hand, have discovered key psychological contributors to physical health. In reality, many conditions cannot be neatly categorised as affecting either ‘mental’ or ‘physical’ health.