The Causes of Depression

There are three basic causes of depression.

1. A family history of depression.
2. Drug or alcohol abuse.
3. Feeling trapped in your life.

Here is a deeper look at each one.

Family History of Depression

Genes explain approximately 30 to 40 percent of depression.[1],[2] Approximately 60 to 70 percent of depression is due to environmental factors and poor coping skills. This has been proven by looking at identical twins, which have the same genes. Genes would explain 100 percent of depression if every time one twin developed depression the other twin also developed depression. But in fact, when one twin develops depression, the other twin develops depression approximately 30 to 40 percent of the time.

Depression is caused by changes in neurotransmitters such as serotonin and dopamine. Your brain has to produce these neurotransmitters to keep your mood balanced. If you have a family history of depression, your brain has a harder time producing those neurotransmitters in the right quantities, which means you are predisposed to depression.

If you think about it, it's a miracle that more people don't get depressed. Your brain has to produce millions of chemicals every day in exactly the right amounts in order to function properly. If it produces some of those chemicals in slightly reduced amounts, or not at exactly the right time, you will feel depressed.

If your main cause of depression is family history, it's more likely you may need antidepressants to overcome depression. A family history of depression is sometimes hard to recognize. Most people don't openly admit that they suffer from depression, and previous generations were reluctant to seek treatment for depression. Sometimes you have to decide if you have a family history, not by what people say, but by how they behave.

Drugs, Alcohol Abuse and Depression

All drugs and alcohol are brain depressants. In moderate amounts, alcohol does not lead to depression, but abusing drugs or alcohol will definitely lead to depression. This is because they deplete your brain of serotonin and dopamine. Brain scans have shown that it can take months for your brain chemistry to return to normal after drug or alcohol abuse.

Alcohol abuse almost doubles the risk of depression.[3]One study looked at 2,945 alcoholics. Fifteen percent were depressed before they began abusing alcohol, and that number jumped to 26 percent after they started abusing alcohol. Once they stopped drinking for an extended period, 15 percent remained depressed. In other words, alcohol almost doubles the risk of depression.

Marijuana users are four times more likely to develop depression.[4] One study followed a large group of people for 16 years. It discovered that people who smoked marijuana were four times more likely to develop depression. This was confirmed by another study of 1601 students.[5]

Even stimulants such as cocaine cause depression. Cocaine initially stimulates your brain, and temporarily elevates your mood. But over the long run it depletes your brain of serotonin and dopamine and leads to depression.

Feeling Trapped

If you feel trapped in your life, you'll struggle against that feeling until you eventually become exhausted and depressed. You can feel trapped by external factors, such as a job that you don’t like or an unhealthy relationship that won’t change. But in many cases you are trapped by internal factors, such as poor self-esteem or negative self-labeling. Feeling trapped is partly why depression can often lead to anxiety and panic attacks.

This is where cognitive therapy helps treat and prevent depression. It helps you see how your negative thinking makes you feel trapped. It helps you see ways that you are not trapped. It also helps you develop alternative thinking so that you can get out of feeling trapped. (Reference: Anxiety and Depression Guide)

Dual Diagnosis

Approximately 15 to 30 percent of addicts suffer from both addiction and underlying depression.[6],[7] The combination of depression and addiction is sometimes called a dual diagnosis. People who have a dual diagnosis often have a repeating pattern of staying sober for a while and then relapsing because they feel awful.

If you have a dual diagnosis and your depression isn't treated, you're more likely to relapse, because your recovery feels flat and unrewarding. If you're depressed for too long, you'll eventually think of turning to your addiction to escape. If you don't have a dual diagnosis, you'll generally start to feel better quickly after you stop using.

Dual diagnosis is hard to diagnose in the first few months of recovery. It's hard to decide if the symptoms of depression are due to an underlying depression or due to the depressant effect of drugs and alcohol. You usually have to be abstinent for at least 3 months before a diagnosis of underlying depression can be made. Sometimes it takes as long as 6 months for your brain chemistry to begin to return to normal. Of course these are general guidelines.

Other Possible Causes

The majority of depression is due to the three basic causes mentioned above. But certain diseases and medications can also cause depression.

For example, depression can be due to anemia, diabetes, thyroid disease, or heart disease. Long-term use of some medications such as high blood pressure pills, sleeping pills, or birth control pills can also lead to depression.

Your doctor may choose to do some blood tests including, complete blood count (CBC), fasting blood sugar, thyroid function, routine electrolytes, vitamin B12, folate levels, and liver function tests, to rule out medical causes for depression.

Also some medical conditions can look like depression. The most common of those is bipolar disorder.

The Difference Between Sadness and Depression

Sadness is an appropriate reaction to a negative event. The difference between sadness and depression is that sadness isn't burdened with negative thinking. If you lose your job, it's normal to feel sad. But if you think that losing your job means that you're a failure, or that you'll never be happy again, then you'll feel depressed.

Because sadness is appropriate, it's temporary. When you're sad, you do things to pick up your spirits. You can talk to friends, get a good night's sleep, do things that you enjoy, and your sadness will get better on its own. Depression usually doesn't get better on its own, and it may get worse if left untreated.

External Links

Alcohol Abuse
Opioid Abuse
Marijuana Abuse
Cocaine Abuse
Benzo/ Tranquilizer Abuse


1) K.S. Kendler, M. Gatz, C.O. Gardner, N.L. Pedersen. "A Swedish national twin study of lifetime major depression," Am J Psychiatry 2006 Jan;163(1):109-14.
2) K.S. Kendler, S.H. Aggen. "Time, memory and the heritability of major depression," Psychological medicine 2001, vol. 31, no5, pp. 923-928.
3) Schuckit MA, Tipp JE, Bergman M, Reich W, Hesselbrock VM, Smith TL. Comparison of induced and independent major depressive disorders in 2,945 alcoholics. American Journal Psychiatry. 1997 Jul;154(7):948-57.
4) Bovasso GB. Cannabis abuse as a risk factor for depressive symptoms. American Journal Psychiatry. 2001 Dec;158(12):2033-7
5) Patton GC, Coffey C, Carlin JB, Degenhardt L, Lynskey M, Hall W. Cannabis use and mental health in young people: cohort study. British Medical Journal. 2002 Nov 23;325(7374):1195-8.
6) Schuckit MA, Tipp JE, Bergman M, Reich W, Hesselbrock VM, Smith TL. Comparison of induced and independent major depressive disorders in 2,945 alcoholics. American Journal Psychiatry. 1997 Jul;154(7):948-57.
7) RC Kessler, WT Chiu, O Demler, EE Walters. Prevalence, severity, and comorbidity of twelve-month DSM-IV disorders in the National Comorbidity Survey Replication (NCS-R). Archives of General Psychiatry, 2005 Jun;62(6):617-27.


Last Modified: March 21, 2018

Information included: Depression symptoms, anxiety and depression, and depression treatment are covered. Learn the causes of depression, understand the symptoms of depression, and discover treatment options. You'll learn about clinical depression, medication, and a test. There's information on what is depression. Learn about depression suicide, support, and therapy. For a more information please look at the book, I Want to Change My Life by Dr. Steven M. Melemis.