A surprising finding published in the most recent issue of Clinical Psychological Science:
Seasonal affective disorder (SAD) is based on the theory that some depressions occur seasonally in response to reduced sunlight. SAD has attracted cultural and research attention for more than 30 years and influenced the DSM through inclusion of the seasonal variation modifier for the major depression diagnosis. This study was designed to determine if a seasonally related pattern of occurrence of major depression could be demonstrated in a population-based study. A cross-sectional U.S. survey of adults completed the Patient Health Questionnaire–8 Depression Scale. Regression models were used to determine if depression was related to measures of sunlight exposure. Depression was unrelated to latitude, season, or sunlight. Results do not support the validity of a seasonal modifier in major depression. The idea of seasonal depression may be strongly rooted in folk psychology, but it is not supported by objective data. Consideration should be given to discontinuing seasonal variation as a diagnostic modifier of major depression.
Here’s one passage from this very interesting paper:
There have been other reports that support this finding and cast doubt on sunlight exposure as a causal factor in depression. Hansen et al. (2008) reported no increase in depression in northern Norway during the twomonth-long “dark period” (p. 121). A large-scale study of residents of Tromsø, Norway, a city north of the arctic circle and also subject to the two-month polar night, found neither an increase in self-reported mental distress during the polar night nor a decrease in reported mental distress during the polar day (Johnsen, Wynn, & Bratlid, 2012).
Zoe Margolis writes in The Guardian a powerful account of how running saved her from depression:
“Every step I have taken in the past few months has been a step away from pain, a step closer to feeling better. When I run, I know that at some point endorphins kick in, positive brain chemistry happens, and I feel brilliant. There is science behind that, obviously, but to me it is a simple equation that needs little explanation: I feel crap, so I run, and afterwards, sometimes for days, my depression lifts. It is not a magical cure, and I’m sure it doesn’t work for everyone, but it keeps a lid on it for me. I never expected running to lessen my depression and am surprised, daily, that it does. For me, it is truly a lifesaver.”
Dr. Greger reviews the evidence:
From Current Directions in Psychological Science:
“Access to calorie-dense foods, medicine, and other comforts has made modern humans healthier than our prehistoric ancestors in many respects. However, the epidemics of obesity, diabetes, and cardiovascular disease suggest that there are also drawbacks to modern living. Here, we address the question of whether the dramatic cultural changes that have occurred over the past century have inflated rates of postpartum depression, adding postpartum depression to the list of “diseases of modern civilization.” We review evidence from cross-cultural, epidemiological, and experimental studies documenting associations between postpartum depression and modern patterns of early weaning, diets deficient in essential fatty acids, low levels of physical activity, low levels of sun exposure, and isolation from kin support networks, all of which mark significant divergences from lifestyles believed to have been typical throughout human evolutionary history. This “mismatch hypothesis” of postpartum depression integrates research across diverse research areas and generates novel predictions.”
An article in Modern Farmer reports on a study linking pesticides with depression in pesticide applicators. Here is the original study. From the results section of the abstract:
“After weighting for potential confounders, missing covariate data, and dropout, ever-use of two pesticide classes, fumigants and organochlorine insecticides, and seven individual pesticides—the fumigants aluminum phosphide and ethylene dibromide; the phenoxy herbicide (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T); the organochlorine insecticide dieldrin; and the organophosphate insecticides diazinon, malathion, and parathion—were all positively associated with depression in each case group, with ORs between 1.1 and 1.9.”
OR is the abbreviation for odds ratio, explained here.
Dr. Greger reviews research on mood state and vegetarian diets: