Lifestyle and habits matter at all points in life. Smoking, heavy drinking, and skipping exercise aren’t just bad habits—they are chipping away at both your physical and mental health well before you hit old age. That’s the message from a new Finnish study, which followed participants from early adulthood into their 60s and found that unhealthy lifestyle choices made in 20s and 30s can already impact your well-being by your mid-30s.

Published in Annals of Medicine, the study offers one of the most comprehensive long-term looks at how everyday behaviors influence health outcomes decades later—not just physically, but mentally too.

“Non-communicable diseases such as heart disease and cancer cause almost three-quarters of deaths worldwide,” says lead author Tiia Kekäläinen, a health scientist specializing in aging. “But by following a healthy lifestyle, an individual can cut their risk of developing these illnesses and reduce their odds of an early death.”

The research is part of a longitudinal study that tracked people born in 1959 in the Finnish city of Jyväskylä. Of those, 326 participants were assessed at age 27 and again at 36, 42, 50, and 61. Researchers measured physical health using a metabolic risk score (based on blood pressure, cholesterol, blood sugar, and waist size) and mental health through surveys on depression symptoms and psychological well-being. Participants also rated their overall health each year.

At each time point, researchers recorded whether participants engaged in three risky behaviors:

• Smoking
• Heavy drinking (defined as over 875 alcohol units per year for women and 1,250 for men)
• Physical inactivity (exercising less than once a week)

The results were striking: even doing just one of these at a single point in time negatively affected physical and mental health. But when all three behaviors persisted over time, the impacts were significantly worse.

Compared to those with healthier habits, participants who engaged in all three behaviors showed significant increases in depressive symptom and metabolic risk as well as significant drops in psychological well-being and self-rated health

Each behavior seemed to impact health differently. Lack of exercise was most strongly linked to physical decline, smoking was closely tied to mental health struggles, and heavy drinking affected both.

“Our findings highlight the importance of tackling risky health behaviors, such as smoking, heavy drinking and physical inactivity, as early as possible to prevent the damage they do from building up over the years, culminating in poor mental and physical health later in life,” Kekäläinen explained.

The study adds nuance by acknowledging that the relationship between behavior and health likely flows both ways. Someone experiencing depression or stress may start drinking more or exercising less to cope, which in turn worsens their health—creating a feedback loop.

The researchers also only tracked three lifestyle factors—whereas diet, sleep, and stress levels were not included, and should be explored in future studies.

While the findings are based on people born in Finland in the 1950s and 60s, the researchers believe they’re still broadly relevant to Western populations. However, newer generations may face different risk profiles shaped by digital habits, processed foods, or work-related stress.

Young people often think they’re invincible to be ravaged by clutches of oldie and that of health habits as something to worry about “later”—but this study makes clear that the path to healthy aging starts is happening to you now no matter how old you are. With this in mind, it’s never too late to turn the ship around, but remember how much the damage has been done when you finally feel the effects of your consequences.

T Kekalainen et al. Cumulative associations between health behaviours, mental well-being, and health over 30 years. Annals of Medicine (2025). https://doi.org/10.1080/07853890.2025.2479233