These Common Bad Habits in Your 30s Can Damage Your Body and Mind for Decades

A new study reveals that smoking, heavy drinking, and inactivity from a young age significantly harm mental and physical health by midlife, urging early lifestyle changes for healthier aging.

Addressing harmful lifestyle choices, such as smoking, excessive alcohol consumption, and physical inactivity, early in life is crucial for increasing the likelihood of a healthy and fulfilling old age.

That’s the key takeaway from a newly published peer-reviewed study in the Annals of Medicine. The research found that behaviors like smoking are linked to both mental and physical health declines beginning as early as age 36.

The effects are particularly pronounced when these habits persist over many years, according to the Finnish research team behind the study. Their work tracked the health of several hundred participants over a 30-year period, offering one of the most comprehensive long-term views to date.

While previous studies have typically followed individuals from middle age onward, usually over a span of about 20 years, this new study stands out by beginning in early adulthood. It also uniquely explores how these lifestyle choices influence not just physical but also mental health over time.

Tracking Health Over Time

Using a long-running longitudinal study, in which hundreds of children who were born in the Finnish city of Jyväskylä in 1959 were followed from childhood until their early 60s, the team analyzed participants’ mental and physical health via data that was collected from surveys and medicals when they were 27 years old (326 participants) and again at age 36, 42, 50 and 61 (206 participants).

Mental health was assessed via surveys on symptoms of depression and on psychological well-being. Physical health was assessed by creating a metabolic risk score based on blood pressure, waist size, and levels of blood sugar, cholesterol, and other blood fats.

Self-health was assessed by asking the participants to rate the state of their health over the past year.

Three risky behaviors were also assessed at each point in time: smoking, heavy drinking (defined as consuming at least 7,000g/875 units of alcohol a year for women and 10,000g/1,250 units a year for men), and physical inactivity (exercising less than once a week).

Key Findings From the Data

The results revealed that individuals who engaged in all three unhealthy behaviors at any single time point had worse mental and physical health compared to those who did not.

Specifically, compared to healthier individuals:

• Depressive symptoms increased by 0.1 points
• Metabolic risk score rose by 0.53 points
• Psychological well-being declined by 0.1 points
• Self-rated health dropped by 0.45 points

Scales used:

• Depressive symptoms and psychological well-being: 1 to 4
• Self-rated health: 1 to 5
• Metabolic risk score: 0 to 5

Long-term engagement in all three risky behaviors was associated with even worse outcomes:

• Depressive symptoms rose by 0.38 points
• Metabolic risk increased by 1.49 points
• Psychological well-being fell by 0.14 points
• Self-rated health declined by 0.45 points

Behavior-Specific Impacts

Lack of exercise was particularly linked to poor physical health, smoking was mainly linked to poor mental health, and heavy alcohol consumption was associated with declines in both mental and physical health.

Crucially, the effects were apparent by the time the participants were in their mid-30s.

“Non-communicable diseases such as heart disease and cancer cause almost three-quarters of deaths worldwide,” says lead author Dr Tiia Kekäläinen, a health scientist who has a particular interest 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.

“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 to from building up over the years, culminating in poor mental and physical health later in later life.

“However, it is never too late to change to healthier habits. Adopting healthier habits in midlife also has benefits for older age.”

The authors note that the study was observational and so couldn’t establish that the risky behaviors were fueling ill health, rather than vice versa.

They say that the relationship is likely two-way. For example, someone who is stressed may drink heavily to help them cope. This could then cause problems with family and friends that lead to poorer mental well-being.

They add that the results are likely to apply to people born in Finland and other Western countries in the late 1950s and in the 1960s. However, they may not be as relevant to younger generations, owing to cultural and societal changes, and partly different risky behaviors occurring nowadays.

The study’s limitations include rating each of the three habits as being equally damaging to health, instead of weighting them.

The authors also acknowledge that they only looked at three types of behavior and say that other factors, such as diet, should be included in future studies.

Reference: “Cumulative associations between health behaviours, mental well-being, and health over 30 years” by Tiia Kekäläinen, Johanna Ahola, Emmi Reinilä, Tiina Savikangas, Marja-Liisa Kinnunen, Tuuli Pitkänen and Katja Kokko, 24 April 2025, Annals of Medicine.
DOI: 10.1080/07853890.2025.2479233

The study was funded by the Finnish Cultural Foundation and the Academy of Finland.

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