As a rule, depression develops from the interplay of various distinct influences. On one hand, there are hereditary factors, which increase the likelihood that the condition will develop over the course of a lifetime. On the other hand, there are sudden triggers that can cause the onset of the illness. How powerfully these factors manifest varies from person to person. Some individuals generally have lower psychological resilience, also known as increased vulnerability, and therefore a higher risk of developing depression.

Those affected often ask whether depression is a "psychological" or a physical illness. As is so often the case, two sides can be observed in every individual suffering from depression: the psychosocial side and the neurobiological side. These two areas are not mutually exclusive, but rather complement each other. This means that depression does not have either purely physical (neurobiological) or purely psychosocial (psychological) causes; instead, causes can always be found on both sides, and treatment can target both.

A major factor in the development of depression is genetic predisposition. Studies show that individuals with a family history of depression have a higher risk of developing the illness themselves. Heritability therefore plays a significant role in one's susceptibility to depression. This means that if a parent is affected by depression, for example, the risk of their children also developing the condition increases. In identical twins, who share identical genetic material, both twins develop depression in about 50% of cases. However, this also demonstrates that genes alone do not provide the full explanation. Additional influences must also come into play.

Biological factors, particularly changes in the brain, can also be among the causes of depression. Researchers have found that individuals with depression frequently experience a disruption in their neurotransmitter balance. Neurotransmitters are chemical messengers in the brain responsible for communication between nerve cells. An imbalance of these substances, such as serotonin, dopamine, and norepinephrine, can trigger depressive episodes.

Examples of biological influences:

• Neurotransmitter imbalance: A well-known example is an imbalance of serotonin levels in the brain, which can lead to mood swings and depressive symptoms. (In German, this referred to as “Serotonin-Syndrom”, not to be confused with the English “Seretonin Syndrome”, referring to a specific, potentially dangerous toxicity caused by a dangerous overdose or interaction of medications.)
• Hormonal changes: Hormones also play a role in the development of depression. For instance, an imbalance in the stress hormones cortisol and adrenaline can increase the risk of depression. Due to hormonal fluctuations, women are more vulnerable to postpartum depression during pregnancy and after childbirth.
• Structural brain changes: Studies have shown that certain brain regions, such as the hippocampus, can be reduced in size in people with depression. The hippocampus is vital for memory and emotions, and changes to its structure can intensify depressive symptoms.

Among the most significant psychosocial causes of depression are stressful life events and chronic strain, which can severely disrupt one's emotional balance. Common triggers of depression include the loss of a loved one, separation or divorce, financial worries, unemployment, or professional pressure. Such life changes often require an intense adjustment period filled with emotional challenges and feelings of being overwhelmed. High workload, job insecurity, and a poor work-life balance can also cause long-term stress and trigger depressive symptoms.

In addition, cognitive and emotional factors play a decisive role in the development of depression. Individuals with low self-esteem, excessive perfectionism, or negative thought patterns, such as "I am worthless" or "I can't handle this", face an increased risk of developing depression. These core beliefs often stem from past distressing or traumatic experiences and become deeply ingrained over the course of a person's development.

Childhood experiences are particularly formative. Traumatic events such as abuse, neglect, violence, bullying, or the loss of a parent can leave profound psychological scars and significantly increase the risk of depression later in life. Another contributing factor can be an adverse developmental environment during childhood. An anxious-overprotective parenting style, resulting in "learned helplessness," as well as poor stress-coping skills, are considered risk factors for depression. Frequently, an overprotective parenting style occurs because parents recognize their child's psychological vulnerability early on and respond by becoming particularly protective.

Alongside individual and familial factors, social influences also impact the development of depression. Social isolation, a lack of support from one's environment, or ongoing conflicts within the family can increase the risk further. Conversely, studies show that stable social relationships, a sense of security, and a loving bond in childhood act as protective factors, strengthening psychological resilience.

Many people report feeling sadder in the late autumn and winter. They usually blame this on the lack of natural daylight and the colder temperatures. For some individuals, however, this sadness is severe enough to be considered a type of depression. This seasonal affective disorder (SAD) frequently occurs in our latitudes during the winter months when daylight decreases. The lack of sunlight can lower vitamin D levels and impair the production of serotonin, which can lead to depressive symptoms.

Furthermore, high temperatures and heatwaves can result in physical stress, sleep disturbances, and increased irritability, thereby elevating the risk of depression. Elderly individuals and those with chronic illnesses, in particular, are increasingly suffering from the impacts of the climate crisis.

Studies show that a high level of noise pollution as well as increasing air pollution, especially in major cities, have a negative impact on mental health. Consequently, these aspects are considered potential intensifiers regarding the development of depression.

Alongside an unhealthy lifestyle, chronic lack of sleep, or regular alcohol consumption, there are other factors that elevate the risk of a depressive episode. These include chronic conditions such as heart disease, diabetes, or cancer. Managing a chronic illness can be emotionally draining and can lead to a negative outlook on life. Prolonged pain and physical disabilities can also act as triggers for depression. Individuals living with chronic pain or physical limitations frequently face a higher risk of developing depressive symptoms.

Being female is considered another risk factor for the development of depression, as current data indicates that women report depression more frequently. The condition manifests differently in women than in men and can be traced back to different causes. Research shows that women are affected by depressive illnesses roughly twice as often as men.

Despite the diverse causes and risk factors for depression, it is important to emphasize that depression is a complex and serious illness that can be treated effectively. Seeking help early on and accepting support is crucial. Alongside traditional forms of therapy, digital options are now available to help individuals find their way out of depression.

You can access early, personalized help with deprexis, a digital therapy program for the treatment of depression. To help you find your way back to greater lightness step-by-step, deprexis supports you with a personalized program, exercises for managing low moods, and practical self-care advice.

deprexis is available to you free of charge with a prescription – the costs are fully covered by your health insurance. This means your doctor or psychotherapist can prescribe deprexis for you, and you will receive an activation code for the program. As soon as you have the code, you can easily redeem it on our website and start using deprexis right away.