Professor Nicholas G. Martin, from QIMR Berghofer Medical Research Institute in Brisbane, Australia, is a world leader in the effort to understand the genetic architecture underlying disordered gambling. This article pays tribute to Nick and his almost two decades of gambling research, highlighting his many strengths, ranging from the use of ingenious recruitment approaches, twin study methods, genomewide association studies, to facilitating international collaborations.

The International Cannabis Consortium (ICC) was founded in 2013 by Jacqueline Vink, Nathan Gillespie, Karin Verweij and Eske Derks. The largest contribution to the first meta-analysis was made by Prof. Nick Martin. The ICC has published two primary publications, in Translational Psychiatry and Nature Neuroscience, and many secondary publications. The study’s principal investigators will always be grateful for Nick’s contribution to science as they would not have been able to do any of this work without the contributions of Nick and others who collected samples. Nick has made unique contributions to the careers of many junior researchers by supporting their development and growth into senior positions.

The study and identification of genotype–environment interactions (GxE) has been a hot topic in the field of human genetics for several decades. Yet the extent to which GxE contributes to human behavior variability, and its mechanisms, remains largely unknown. Nick Martin has contributed important advances to the field of GxE for human behavior, which include methodological developments, novel analyses and reviews. Here, we will first review Nick’s contributions to the GxE research, which started during his PhD and consistently appears in many of his over 1000 publications. Then, we recount a project that led to an article testing the diathesis-stress model for the origins of depression. In this publication, we observed the presence of an interaction between polygenic risk scores for depression (the risk in our ‘genotype’) and stressful life events (the experiences from our ‘environment’), which provided the first empirical support of this model.

Identification of genetic variants associated with eating disorders is underway. The Anorexia Nervosa Genetics Initiative, an initiative of the Klarman Family Foundation, has contributed to advancing the field, yielding a large-scale genome-wide association study published in Nature Genetics. Eight genetic variants significantly associated with anorexia nervosa were identified, along with patterns of genetic correlations that suggest both psychiatric and metabolic origins of this serious and life-threatening illness. This article details the role of Professor Nick Martin in contributing to this important collaboration.

I recount early formative experiences with my father, Nick Martin.

This article opens with the brief life histories of reared-apart monozygotic (MZ) male twins. A New York City program that helped childless couples conceive via artificial insemination from the 1930s to the 1950s is examined as it related to these twins. The frequency with which pregnancies following assisted reproductive technology resulted in MZ twin pairs is also provided. Next, summaries of twin research concerning selective resuscitation, gene editing, sexual arousal and jejuno-ileal atresia are presented. The article ends with media reports of twin girls’ efforts to find a bone marrow donor for their father, possible parasitic twinning in a puppy, identical female twins’ business venture, the surgical separation of craniopagus twins, a twin-themed magazine cartoon and tragic events involving identical male twins.