Contact Information



I am currently an Assistant Professor in the Department of Psychology, Neuroscience & Behaviour at McMaster University in Ontario.

I was trained in behavioral ecology at the University of New Mexico (UNM), Department of Biology, but I am somewhat unusual in that I worked on human behavior and psychology as part of my PhD dissertation. So I may call myself a behavioral ecologist, an evolutionary biologist, or an evolutionary psychologist, depending on the situation.

My primary research interest is understanding the evolution of depression. Andy Thomson and I published a paper in Psychological Review that argues depression is an evolved emotional response to complex problems, and its function is to promote changes in body systems that promote analysis of those problems. A pdf of the manuscript can be downloaded below. We wrote a short piece describing our work for Scientific American's blog, "Mind Matters". You can read it here. This piece, and the longer Psychological Review article were criticized by Jerry Coyne in Psychiatric Times, which you can read here (you'll have to register to see it, but registration is free). We published a response to Coyne's piece in the same journal, which you can read here. Also, our work was the subject of a featured article in the New York Times Sunday Magazine, which you can see here.

My most recent work on depression, published in the on-line, open-access journal Frontiers in Psychology, examines the risk of relapse after discontinuing antidepressant medication. You can download the article for free here. Serotonin and norepinephrine are important neurotransmitters in the brain that have broad effects on how we think, feel, and behave, and they are thought to be involved in depression. Antidepressant medications attempt to reduce depressive symptoms by altering the levels of these neurotransmitters in the brain. My colleagues and I found evidence that the brain pushes back against antidepressant drugs in an attempt to keep serotonin and norepinephrine at their pre-medication levels. When one stops taking antidepressant medications, the pressure causes an overshoot of symptoms, which corresponds to an increased risk of relapse--greater than the risk if one had not taken antidepressant medications in the first place. This work suggests that antidepressants can leave people stuck in a cycle where they have to continue taking the drugs to prevent a return of symptoms.

I also work on sexual infidelity, suicidal behavior, and other mental health traits from an evolutionary perspective. Other aspects of my research involve evolutionary metatheory (e.g., how to test and choose between adaptationist and non-adaptationist hypotheses for traits), and developing statistical methods for estimating underreporting (UR) and overreporting (OR) from multi-rater datasets.

Here are some of my publications:

Andrews, P. W., Kornstein, S. G., Halberstadt, L. J., Gardner, C. O. & Neale, M. C. (2011). Blue again: Perturbational effects of antidepressants suggest monoaminergic homeostasis. Frontiers in Psychology, 2, 159. doi: 10.3389/fpsyg.2011.00159. Andrews_FP_2011

Andrews, P. W., & Thomson, Jr., J. A. (2009). The bright side of being blue: Depression as an adaptation for analyzing complex problems. Psychological Review, 116(3), 620-654. Andrews_PR_2009

Andrews, P. W., Gangestad, S. W., Miller, G. F., Haselton, M. G., Thornhill, R., & Neale, M. C. (2008). Sex differences in detecting sexual infidelity: Results of a maximum likelihood method for analyzing the sensitivity of sex differences to underreporting. Human Nature, 19(4), 347-373.

Andrews, P. W. (2006). Parent-offspring conflict and cost-benefit analysis in adolescent suicidal behavior: Effects of birth order and dissatisfaction with mother on attempt incidence and severity. Human Nature, 17(2), 190-211. Andrews_HN_2006

Andrews, P. W., Gangestad, S. W., & Matthews, D. (2002). Adaptationism - How to carry out an exaptationist program. Behavioral and Brain Sciences, 25(4), 489-504. Target article. Andrews_BBS_2002

Recommended Websites:
Ed Hagen's blog that defends adaptationism, "Dr. Pangloss"
Paul Watson, behavioral ecologist extraordinaire
Stephen Stearns' excellent advice for graduate students