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Risk Factors

Despite decades of research, experts still don’t know why depression afflicts some people and not others. Two people can have very similar backgrounds, experience similar challenging events, and yet one develops depression and the other does not. Even people who have every reason to be happy and have no obvious precipitating event or risk factor for depression still develop it at times, while those who seem to have all the cards stacked against them never become depressed.

The underlying cause of this common psychiatric disorder, in the vast majority of cases, is most likely a combination of different factors rather than one single thing. For some individuals, there may be an obvious cause such as a precipitating event that triggers the disorder. For others, the cause may be the cumulative effect of multiple stressors combined with a genetic or biological predisposition.

Let’s take a closer look at some of the different things that may make you or a loved one vulnerable to depression.


Individuals who have a close relative with depression have a greater risk of developing the disorder. This doesn’t mean that all family members are destined to develop it, however. In some families, only one person develops depression. Although scientists continue to explore the role of genetics in depression, they have not identified a specific “depression” gene. But genetics most likely play a role in some – if not many – cases. A genetic predisposition can be an underlying factor – greatly increasing the risk when combined with other things like substance abuse, childhood trauma, or severe stress.

The fact that some types of depression runs in families may not always be due to genetics, however. Family members experience many of the same environmental factors that can increase the risk for depression, such as a high degree of conflict in the home, low socioeconomic status, trauma (for example, physical or sexual abuse within the home), and so on.

Also, personality aspects related to depression – such as low self-esteem, pessimism, fearfulness, dependency, negative thinking, and / or a sense of helplessness – are typically learned at home. Children who grow up in homes that foster these traits are typically more vulnerable to depression than their peers raised in healthier environments.

Major Life Stressors

A variety of life events and stressors can trigger depression in some people. Any kind of significant loss, such as the death of a loved one, divorce, a breakup, or a serious financial loss, can cause a depressive episode. This may be due to the beliefs associated with the loss (e.g. believing one is worthless or a failure) as well as the physiological impact of the stress (e.g. severe stress increases cortisol, which impacts serotonin and other brain chemicals). Exposure to chronic conflict can also lead to depression.

Trauma can also trigger depression. Women who are battered and children who are abused physically and / or sexually are much more vulnerable to depression than those who do not experience similar trauma.

Even events that are generally regarded as positive things – e.g. a promotion, getting married, or having a baby – can trigger depression. Postpartum depression is not uncommon following childbirth – and may be due to a combination of hormonal factors, stress, and lack of sleep.

Biological Factors

Studies show that biology likely plays a role in most cases of depression. This can include brain chemistry, brain abnormalities or changes, and hormonal factors.

Brain chemistry involves certain chemicals – known as neurotransmitters – that help regulate mood, appetite, sleep, and emotions. Serotonin and norepinephrine are two neurotransmitters that often play a role in depression (although there are many others that may as well). When these chemicals are out of balance, depression may be the result. This is why antidepressant medications – which help balance brain chemicals – can be helpful in the treatment of depression for some people. Most of the popular medications for depression are SSRIs – which stands for “selective serotonin reuptake inhibitors”. However, antidepressants don’t work for everyone which suggests that brain chemistry is only one of many causes.

Brain changes or abnormalities may also cause depression. For example, researchers have found that individuals with a thin right cortex or a small hippocampus are more likely to develop depression.

Hormonal factors also play a role in depression. Hormonal differences between men and women may be one of the reasons that women tend to be twice as likely to develop depression as men. Studies have also shown that people who struggle with depression often have high levels of cortisol, a hormone associated with stress.

Often, these biological factors are intertwined. Excess cortisol can impact the hippocampus, for example. High levels of stress can also lead to imbalances in serotonin and other neurotransmitters.


Certain medications can cause depression, particularly when taken for extended periods of time. These include beta-blockers (for heart conditions and migraines; e.g. Lopressor), benzodiazepines (e.g. Xanax), anticonvulsants (for seizures), corticosteroids (e.g. prednisone), statins (to lower cholesterol; e.g. Lipitor), opioids (for pain; e.g. codeine, OxyContin), estrogens (e.g. Premarin), barbiturates, calcium-channel blockers (used for heart conditions; e.g. Cardizem), and antabuse.

Other medications include eBromocriptine (for Parkinson’s disease), Accutane (for severe cases of acne), Zovirax (for shingles and herpes), Norplant (for birth control), Interferon alfa (for hepatitis B and certain types of cancer), and fluoroquinolone antibiotics (e.g. Cipro).

Medical Conditions

Certain types of medical conditions, as well as chronic illness, chronic pain, and life-threatening illness can all cause symptoms of depression. These include cancer, diabetes, brain trauma, allergies, Alzheimer’s disease, hypothyroidism, Huntington’s disease, multiple sclerosis, perimenopause, stroke, heart disease, and Parkinson’s disease.

Personality Factors

Personality plays a role in developing depression. As mentioned above, certain personality characteristics make individuals particularly vulnerable to depression. These include low self-esteem, a sense of helplessness, a pessimistic outlook, negative thought patterns, a tendency to worry constantly, and the inability to handle rejection.

Co-morbid Psychiatric Disorders

Individuals with other psychiatric disorders are often much more vulnerable to stress. While the co-morbid disorder itself doesn’t necessarily cause depression, the challenges that accompany a mental illness can trigger depression. Frequent co-morbid disorders include schizophrenia, borderline personality disorder, obsessive-compulsive disorder, social anxiety, and panic disorder.

Substance Abuse

When it comes to substance abuse, it can sometimes be difficult to determine whether depression led to the abuse (i.e. the person is self-medicating), or if the substance itself caused the depression. That being said, certain substances, such as alcohol, can cause depression when used regularly.

Nutritional Deficiencies

Research has shown that certain deficiencies in the diet may contribute to symptoms of depression. These include thiamine (vitamin B1), pantothenic acid (vitamin B5), vitamin B12, vitamin B6, and folic acid. Low fat diets – particularly a deficiency in Omega-3 fatty acids – have also been associated with increased risk for depression.

As you can see, there are many different potential causes of depression. This is why it is often so difficult to pinpoint the exact cause. And, as mentioned above, it is generally the result of a combination of factors rather than just one. That being said, it is helpful to narrow down the most likely potential causes as this will help determine the most effective course of treatment.