A new study on a large sample of mothers and daughters provides evidence that mothers with healthier lifestyles tend to have daughters with fewer depressive symptoms. The link appeared to be achieved through the healthy lifestyles of daughters. But this association was not present in sons. The study was published in Psychological Medicine.
The prevalence of depression among adolescents had seen an increase in recent years. In the United States, estimates show that 8.7% of adolescents had a depressive episode in the past 12 months in 2005, but this percentage grew to 11.3% in 2014. Around half of adolescents diagnosed with depression or major depressive disorder, as it is officially called, also suffer from other psychiatric disorders. In adults, depression is one of the leading causes of disability worldwide.
While there are biological factors that increase the risk of depression, a growing body of scientific research shows that modifiable healthy lifestyle factors can reduce depression risk. “A healthy diet, non-smoking, being physically active, having a normal body mass index (BMI), and light-to-moderate alcohol consumption are independently associated with less depressive symptoms among adults,” wrote Wei-Chen Wang and colleagues in their study.
The researchers wanted to investigate whether the lifestyle of mothers during their offspring’s childhood and adolescence might be associated with depression in their children. They defined the healthy lifestyle of mothers in terms of eating a healthy diet, having a normal body-mass index, never smoking, being physically active, and having light-to-moderate alcohol consumption.
They analyzed data of 10,368 mothers, all nurses by profession, who participated in the Nurses’ Health Study II (which started back in 1989 and has collected data on multiple occasions since) and of 13,478 of their offspring (participants of the Growing Up Today study). Mothers were between 25 and 45 years old at the start of data collection.
Data on the height, weight, and smoking habits of participants were collected using questionnaires every two years. Diet was assessed using the Food Frequency Questionnaire. Questions about alcohol consumption were included in it.
Based on data from this questionnaire, researchers calculated the Alternate Healthy Eating Index 2010 diet score that “consists of the information on vegetables, fruit, whole grains, nuts and legumes, long-chain omega-3 fatty acids, polyunsaturated fatty acids, sugar-sweetened drinks, and fruit juice, red and processed meat, trans-fats, and sodium consumption.”
Participants physical activity was assessed using a questionnaire that asks about the amount of time spent in a number of different physical activities.
Depressive symptoms of offspring were assessed using the Center for Epidemiological Studies Depression Scale-10 (CESD-10) on five occasions between 2010 and 2016. The researchers also obtained information of offspring’s height, weight, physical activity, diet, and smoking used them to make assessments of lifestyle health.
Results showed that mothers with higher healthy lifestyle scores (i.e., with healthier lifestyles) tended to have children with lower depression scores. This association was stronger in older children. Looking at components of the healthy lifestyle, mothers with normal body mass index had children with lower depression scores compared to overweight and obese mothers. The children of mothers who never smoked and who had at least 150 minutes of moderate or vigorous physical exercise per week also had lower depression scores.
When sex of offspring was considered, results showed that the detected associations between healthy lifestyles of mothers and depression of offspring persisted only in daughters. Maternal healthy lifestyle scores were not associated with depression scores of their sons.
Further analysis showed that maternal healthy lifestyle scores were associated with healthy lifestyle scores of their offspring and that it is possible that the link between maternal healthy lifestyle and offspring’s depression is achieved through the healthy lifestyles of offspring.
“Mothers’ lifestyles and behaviors are strongly related to their offspring’s lifestyles,” the study authors concluded. “Offspring of mothers with a healthier lifestyle adhere to a healthier lifestyle later in life. There are several mechanisms potentially underlying this long-term impact of maternal lifestyles. One is through the role modeling process; that is, children adopt their parents’ lifestyle behaviors when establishing their behaviors.”
“Another theory is the mimicry effect; children copy their parents’ behaviors unwittingly and turn them into their norms. Apart from parents passively influencing their children’s behaviors, parenting style, monitoring, and content could also considerably impact offspring’s healthy lifestyles throughout childhood, adolescence, and even adulthood through guidance and joint activities.”
The study sheds light on important psychological mechanisms underpinning the development of depression. However, it should be noted that it relied on self-reports and all participants were nurses by profession. Results on the general population might be different. Additionally, the study design does not allow any cause-and-effect conclusions and some factors included in the healthy lifestyle index are at least partially genetically determined (body mass index), while others depend at least partially on the physical health of the person (physical activity).
The study, “Maternal adherence to healthy lifestyle and risk of depressive symptoms in the offspring: mediation by offspring lifestyle”, was authored by Wei-Chen Wang, Ming Ding, Susanne Strohmaier, Eva Schernhammer, Qi Sun, Jorge E. Chavarro, and Henning Tiemeier.