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What affects depression? How biology, experiences and circumstances interact

Depression does not have one single cause. The way we feel and function is shaped by interacting influences – from our biology and physical health to our relationships, experiences and the environments around us.

In this blog, we look at this bigger picture and explore five interconnected areas: sleep, food, movement, social connection and stress. We consider what research suggests about their relationship with mental wellbeing and depression, as well as realistic ways to support wellbeing.

Important

If you are concerned that you or someone you know may be experiencing depression, consider seeking professional advice. This article is not intended to diagnose or treat depression. Changes to everyday habits may support wellbeing, but they do not replace assessment or treatment.

If you need urgent help for your mental health, use NHS 111 online or call 111 and select the mental health option. If you or someone else needs emergency help, call 999 or go to A&E. You can also speak to your GP.

What affects depression?

Our mental health can be influenced by a combination of biological, psychological, social and environmental factors. These factors interact rather than operating independently.

For example, ongoing stress can disturb sleep. Poor sleep can make it harder to regulate emotions and manage stress. Loneliness can affect mood, while depression can make it harder to connect with other people. Changes in sleep, appetite or activity can also be symptoms or consequences of depression.

It is therefore usually more helpful to ask how different influences interact over time than whether one particular factor causes depression.

Experiencing a particular vulnerability factor does not mean that someone will develop depression. People have different combinations of experiences, circumstances and protective factors, and these can change throughout life.

Understanding the bigger picture: the Vulnerability Factors and Mechanisms Model

YPMH’s Vulnerability Factors and Mechanisms (VFM) model provides a framework for understanding how different influences can come together over time.

The model considers four broad areas:

  • Wider environments and relationships – including family and peer relationships, schools and workplaces, income, housing, food access and community conditions.
  • Individual factors and experiences – including physical health, sleep, dietary patterns, movement, stress and loneliness.
  • Biological mechanisms – processes within the body that may help explain how experiences and circumstances affect mental health.
  • Psychological factors – including patterns of thinking, how we cope with difficulties, our sense of control and the support we feel is available.

These areas are connected. Financial difficulties or problems at school, for example, may contribute to ongoing stress. Stress may disturb sleep, while poor sleep may make it harder to cope with further challenges. Supportive relationships may help someone manage those difficulties.

The relationship can also work in the other direction. Depression can affect sleep, appetite, activity, relationships and responses to stress, creating feedback loops between different parts of our lives.

The VFM model is an explanatory framework, not a diagnostic or predictive tool. It does not tell us who will develop depression or suggest that any one factor has the same importance for everyone.

Explore the science more in depth: Read Changing Minds, Changing Lives →

The circumstances around us matter

The VFM model helps show why mental health cannot be reduced to individual choices.

It can be tempting to discuss sleep, food, movement or stress as though everyone has the same opportunities to make changes. In reality, having enough money to buy nutritious food, somewhere safe to be active, time to rest, supportive relationships and a secure place to live all affect what is possible.

Schools, colleges and workplaces can influence stress, routine, belonging and opportunities for connection. Communities affect access to green space, physical activity and social support. Digital environments can support connection but may also affect wellbeing. Discrimination, bullying and social exclusion can contribute to sustained stress.

Improving mental health is therefore not simply about asking individuals to make better choices. Supportive families, schools, workplaces, communities and wider systems help create the conditions in which good mental health can develop.

Five interconnected areas that can affect mental wellbeing

  • Sleep – regular, good-quality sleep supports emotional and physical health.
  • Food – a varied, nutrient-dense diet supplies the energy, nutrients and other compounds needed by the brain and body.
  • Movement – regular physical activity can support mood, sleep, stress regulation and physical health.
  • Social connection – safe, supportive relationships can help us cope with difficulties and feel that we belong.
  • Stress – short-term stress is part of life, but prolonged stress without sufficient opportunity for recovery can affect physical and mental health.

These areas affect one another and interact with the biological and psychological processes involved in mental health.

How does sleep affect mental health?

Sleep is one of the foundations of physical and mental wellbeing. Good-quality sleep supports emotional regulation, concentration and memory. It is also closely connected with the body’s stress-response system and circadian rhythms, which help regulate the sleep–wake cycle and coordinate processes throughout the body.

The relationship with mental health works in both directions. A systematic review and meta-analysis of longitudinal studies found that insomnia predicted the later onset of depression and some other mental health problems, although the underlying studies had limitations. Depression and other mental health problems can also make it harder to sleep. This can create a cycle in which poor sleep affects mood and low mood affects sleep.

That does not mean every restless night is a cause for concern. Sleep changes throughout life, and illness, stress, school, work and changes in routine can all affect it.

What can you try?

Where possible, aim for a broadly consistent sleep and wake time. Other things that may help include:

  • keeping your bedroom comfortable, quiet and dark where possible
  • having a relaxing wind-down routine before bed
  • getting natural light and being active during the day
  • avoiding caffeine later in the day if it affects your sleep
  • reducing activities immediately before bed that leave you feeling particularly alert or stressed

If sleep problems continue or significantly affect everyday life, consider speaking to a healthcare professional.

Want to know more about sleep and mental health?

Explore our detailed guide to sleep, including practical ways to support better sleep and information about how sleep and mental wellbeing are connected.

Sleep and mental health →

How are food and mental health connected?

Food supplies the energy, macronutrients, vitamins, minerals, fibre and plant compounds that the brain and body need to function. A varied diet based largely on whole and minimally processed foods can support brain and overall health.

Dietary patterns may affect processes relevant to mental health, including metabolism, inflammatory activity and communication along the gut–brain axis. What we eat is also shaped by food availability, affordability, time, cooking facilities, culture and personal needs.

Food connects with the other areas explored in this article. Eating patterns can affect energy and sleep, while stress and low mood can change appetite, eating habits and the motivation to prepare food.

No single food can prevent or treat depression. However, there are good reasons to support a nutrient-dense, fibre-rich dietary pattern and reduce reliance on ultra-processed foods (UPFs). Prospective cohort research has associated higher UPF consumption with a greater risk of depression, while SACN’s rapid evidence update found consistent associations with adverse health outcomes, including mental health conditions. However, the evidence is predominantly observational and cannot by itself prove cause and effect.

Why reduce ultra-processed foods?

Diets dominated by UPFs often provide less dietary diversity and displace fibre-rich, micronutrient-dense plant foods. Several related issues may help explain the concern:

  • Fewer micronutrients and plant compounds. Many UPFs provide substantial energy while containing relatively low levels of vitamins, minerals and phytonutrients. When they displace nutrient-dense foods, the overall diet may provide less of what the brain and body need.
  • Too little diversity of plant fibre. Wholegrains, vegetables, fruit, beans, lentils, nuts and seeds provide different fibres and plant compounds. Diets dominated by UPFs often contain fewer and less varied plant foods, limiting the range of substrates available to gut microorganisms.
  • Inflammatory effects. Human studies have associated higher UPF consumption with increased markers of systemic inflammation. Many UPFs also combine refined starches or free sugars with saturated fat and salt while providing little fibre, contributing to a dietary pattern that may promote inflammatory activity.
  • Additives, gut microorganisms and the intestinal barrier. Experimental research suggests that some additives used in UPFs may affect gut microorganisms and the intestinal environment. In a small controlled-feeding study in healthy adults, the emulsifier carboxymethylcellulose altered gut microbiota composition and metabolites, with microbiota encroachment towards the intestinal lining observed in two participants. These findings cannot be generalised to all additives or usual dietary exposures. People consume mixtures of additives, and their combined long-term effects are not yet well understood.

UPFs are a broad category and individual products differ. This does not remove the concern about a diet dominated by them. It means the most useful approach is to reduce overall reliance on UPFs where practical and replace them with a wider range of nutrient-dense, minimally processed foods.

What can you try?

  • Include more and different plant foods. Choose from vegetables, fruit, wholegrains, beans, lentils, nuts, seeds, herbs and spices. Variety helps provide a wider range of nutrients, fibre and phytonutrients.
  • Choose whole or minimally processed foods more often. These can form the basis of a balanced, nutrient-dense diet.
  • Include sources of omega-3 fats. Oily fish such as salmon, sardines and mackerel provide the long-chain omega-3 fats EPA and DHA. Walnuts, chia seeds and flaxseeds provide the plant omega-3 fat ALA.
  • Reduce UPFs where practical. You do not need to eliminate every UPF. Start with the products you eat most often and make realistic swaps towards foods that provide more micronutrients, plant fibre and nutritional value.

You do not have to eat perfectly. Small changes that make your everyday diet more varied and nutritious can be a useful place to start.

Want to know more about food and mental health? Explore our guide to food, nutrition and mental health, including how dietary patterns can support the brain, body and gut microbiome.

Food, nutrition and mental health →

You can also learn more about the relationship between the gut microbiome, gut health and mental health.

The gut microbiome and mental health →

How does movement affect mental health?

Regular physical activity is associated with better mood and can support sleep, stress regulation and physical health. Being active can also provide a sense of achievement, structure, enjoyment and opportunities to spend time with other people.

Movement does not have to mean going to the gym or taking part in competitive sport. Walking, cycling, dancing, gardening and being more active during everyday life can all be valuable.

The relationship with depression works in both directions. Depression can affect motivation, energy and enjoyment, making activity feel much harder. Reduced activity may then mean fewer opportunities to experience its physical, psychological and social benefits.

Opportunities to be active also depend on access to safe spaces, affordable activities, supportive environments and time away from other demands.

What can you try?

There is no need to move immediately from doing very little to intense exercise. Start with something realistic and, where relevant, suited to your health and mobility. You could:

  • take a short walk
  • walk or cycle part of a journey
  • put on some music and dance
  • spend time gardening
  • try an activity you enjoy or something new

The best activity is often one that feels manageable and enjoyable enough to continue. For adults with depression, NICE includes group exercise among the treatment options that may be considered, depending on individual needs, clinical circumstances and preferences

Want to know more about movement and mental health? Explore our detailed guide to physical activity and mental health, including how movement can support mood, sleep and overall wellbeing.

Explore how exercise supports mental health →

How does social connection affect mental health?

Feeling safely connected to other people is an important part of mental wellbeing. Supportive relationships can provide emotional and practical help and make it easier to cope with difficult experiences.

Loneliness and social isolation are related but different. Loneliness is the feeling that our relationships do not meet our needs, while social isolation refers more to the amount of contact someone has with other people. Someone can have frequent contact and still feel lonely, or have relatively little contact without feeling lonely.

The relationship with depression can work in both directions. Depression can make it harder to maintain relationships or find the motivation to spend time with other people. Withdrawing from activities can then increase loneliness and reduce opportunities for support.

The quality and safety of relationships matter, not simply the number of people someone knows. Family life, friendships, schools, workplaces, communities and digital environments all affect opportunities for connection and belonging.

What can you try?

Connection does not have to mean becoming much more socially active overnight. You could:

  • send a message to someone you trust
  • arrange a walk or coffee with a friend
  • spend time doing an activity with someone else
  • tell someone how you are feeling

If loneliness is persistent or is affecting your mental health, reaching out for support can be an important first step.

Want to know more about social connection and mental health?

Explore our guide to loneliness, social connection and mental health, including why supportive relationships matter for wellbeing.

Social connections and mental health →

How does stress affect mental health?

Stress is a normal part of life. In the short term, the body’s stress-response system helps us respond to situations that require attention or action. Difficulties can arise when stress is prolonged and there is too little opportunity to recover.

Our circumstances can create sources of stress, while coping strategies, sense of control and perceived support can influence how we respond. Prolonged stress can disturb sleep, affect relationships and make it harder to stay active or maintain healthy routines.

Depression can also affect how we experience and respond to stress, potentially making everyday challenges feel more difficult.
Managing stress is not always within an individual’s control. Financial difficulties, insecure housing, discrimination, bullying, difficult family circumstances and excessive demands at school or work may require support from other people or changes to the wider environment.

What can you try?
If you can, identify one source of stress over which you have some control and one for which you may need support. Recovery might involve rest, movement, time outdoors, an enjoyable activity or talking to someone you trust.

If the source of stress is outside your control, asking for help may be more useful than trying to manage everything yourself.

Want to understand more about stress and the body?

Read more →

How do these areas connect with depression?

Sleep, food, movement, social connection and stress are connected to one another and to wider biological and psychological processes. Research is exploring how these experiences relate to the stress-response system, immune and inflammatory activity, hormones, the gut microbiome and brain function.

The pathways can work in both directions. Stress can affect sleep, while poor sleep can make stress harder to manage. Depression can affect sleep, appetite, activity and relationships, creating feedback loops. How we cope, the control we feel we have and the support available to us can influence these relationships.

These pathways are complex and do not operate in the same way for everyone. This is why no single lifestyle change can guarantee that depression will be prevented or resolved.

Want to explore one of these biological pathways in more detail? Learn about the link between inflammation and mental health.

Inflammation and mental health →​

Start small: changes that may support wellbeing

There is no need to change everything at once. A small, realistic change may be easier to maintain than a long list of goals.

You might begin with a short walk, add another plant food to a meal, replace one frequently eaten UPF, make your sleep and wake times more consistent, contact someone you trust or create more opportunity to recover from stress.

What is realistic will differ from person to person. Circumstances can make some changes easier or harder, and asking for support may sometimes be the most useful step.

Conclusion

Depression does not have one single cause. Mental health is shaped by interacting biological, psychological, social and environmental influences, and the VFM model helps us understand how these parts of our lives can connect over time.

Sleep, food, movement, social connection and stress matter, but they are only part of the picture. They affect one another, interact with processes in the brain and body and are shaped by wider circumstances.

Small changes can support wellbeing, but they are not a guarantee against depression and do not replace professional support or treatment. Creating environments in which people have the resources, relationships, safety and opportunities they need matters too. If you are struggling, you do not have to manage it alone.

Sources:

SACN processed foods evidence update (2025); JAMA Network Open UPF and depression cohort study (2023); systemic inflammatory biomarkers review (2025); carboxymethylcellulose controlled-feeding study (2022); insomnia systematic review and meta-analysis (2019); and NICE guideline NG222 on depression in adults.

FAQs

Depression does not have one single cause. Different combinations of biological, psychological, social and environmental influences can affect vulnerability, including genetics, physical health, experiences, relationships, prolonged stress, patterns of behaviour and living circumstances.

There is a two-way relationship between sleep and mental health. Persistent sleep problems are associated with greater vulnerability to depression, while depression can also disturb sleep. Regular, good-quality sleep can support wellbeing but cannot guarantee that depression will be prevented.

A varied, nutrient-dense dietary pattern can support brain, physical and mental health. Diets high in UPFs have been associated with a greater risk of depressive symptoms, but diet alone should not be presented as a treatment for depression. It should complement, not replace, appropriate professional support and treatment.

Regular physical activity can support mood and wellbeing. For some adults with depression, a structured exercise programme can be one element of treatment. What is suitable will depend on the person’s health, circumstances and preferences.

Prolonged stress can interact with sleep, relationships and biological stress-response systems. Supportive relationships can help people cope with difficult experiences. Depression can also lead to withdrawal and loneliness, so these relationships can work in both directions.

If low mood or other symptoms persist, significantly affect everyday life or cause concern for you or someone else, seek professional support. You do not need to wait until things become severe before asking for help. If help is needed urgently, contact NHS 111; if anyone is in immediate danger, call 999 or go to A&E.

Where to get help

If you need further advice on supporting yourself or a young person with their mental health, take a look at the services below that can help.

Looking for local support?

If you’re based in the East of England, these NHS wellbeing hubs offer free tools, advice and services to support your mental health:

Cambridgeshire and Peterborough Wellbeing Hub (H.A.Y)

Suffolk Wellbeing Service

You can find self-help guides, local activities, talking therapies and more.

Samaritans

Whatever you’re going through, you can contact the Samaritans for support. N.B. This is a listening service and does not offer advice or intervention.

Opening times: 24/7
Text: 116123
jo@samaritans.org

Parenting Mental Health

Digital support community and charity offering information, peer support, facilitated listening circles, mentoring and courses for parents of children with mental health difficulties

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