A massive new study published in the journal Nature last December came to the surprising conclusion that, “Psychiatric disorders display high levels of comorbidity and genetic overlap, challenging current diagnostic boundaries.”

The paper, entitled “Mapping the genetic landscape across 14 psychiatric disorders,” was written up by Dr. Mark Gold, the Addiction Outlook editor for Psychology Today. Dr. Gold calls the paper “a turning point,” showing that “many common psychiatric diagnoses are not genetically separate diseases.”

This would be stunning scientific support for “A Unified Theory of Addiction,” a review article by Dr. Robert Pretlow, publisher of AddictionNews, that is still in preprint. In the abstract, Dr. Pretlow states:

[…] the universal source of addiction is the displacement mechanism, and that treatments that quiet this displacement should work with every addiction and compulsive behavior.

The Nature study sports more than 50 co-authors led by Dr. Andrew Grotzinger of the Institute for Behavioral Genetics at the University of Colorado Boulder. “The largest and most detailed analysis to date of how genes influence mental illness,” involved researchers from the Psychiatric Genomics Consortium. They studied 14 childhood- and adult-onset psychiatric disorders involving over one million cases, and compared the results with five million subjects with no diagnosed disorders.

The researchers explain:

Using genetic association data from common variants, we identified and characterized five underlying genomic factors that explained the majority of the genetic variance of the individual disorders (around 66% on average) […]

Dr. Gold tries to condense the implications of these discoveries: “Cross-disorder psychiatric genomics shows high comorbidity and genetic overlap.” The 14 diagnoses separate into five genetic clusters. Within these clusters, patients often have multiple disorders and move between them.

One genetic cluster, say researchers, involves schizophrenia and bipolar disorder. Another cluster involves major depression, post-traumatic stress disorder (PTSD), and anxiety. Yet another cluster involves anorexia nervosa, Tourette’s Syndrome, and obsessive/compulsive disorder (OCD). The clusters show “high levels of polygenic overlap,” say the researchers, “with local genetic correlation and very few disorder-specific loci.”

Dr. Gold is again blunt in estimating the importance of the Nature study: “These findings challenge the disease model in psychiatric diagnoses and the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).” In particular, they call into question whether these are separate disorders, as DSM-5 treats them, a single unified disorder.

Substance use disorder (SUD) is another unified category, according to this analysis, that includes “alcohol, cannabis, opioid, and nicotine use disorders.” Dr. Gold again lays it out: “[S]ome individuals are more susceptible to developing SUDs, regardless of which drug they encounter first.”

In his paper on a unified theory of addiction, Dr. Pretlow explains how addiction results from the need to displace stress, which seeks an outlet. The outlet could be eating, or taking pain-numbing drugs, or running, or cursing. Anything done to relieve stress can become a dependency. Dr. Pretlow writes:

If displacement theory is accurate and provides a unified theory of addiction, the distinction between substance and behavioral addictions may be moot.

Dr. Gold writes, “Addiction is best viewed as a chronic, relapsing brain disease rather than a behavioral problem. […] Like diabetes or hypertension, addiction requires ongoing monitoring, medication when indicated, behavioral intervention, and relapse prevention.”

If Dr. Gold is correct, this new study could lead to changes in the DSM, which treats each of these disorders as a separate disease. And if Dr. Pretlow is correct, this study lends scientific weight to his theoretical article on displacement and the unity of all addictions, the founding basis for AddictionNews.

Written by Steve O’Keefe. First published February 2, 2026.

Sources:

“Mapping the genetic landscape across 14 psychiatric disorders,” Nature, December 10, 2025.

“Very Different Psychiatric Diagnoses Share Common Genes,” Psychology Today, January 22, 2026.

“Sweeping study shows similar genetic factors underlie multiple psychiatric disorders,” CU Boulder Today, December 10, 2025.

“A Unified Theory of Addiction,” Preprint 5, March 9, 2023.

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