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What Causes Depression?

Medically Reviewed and Edited by 
Olga Kyrychenko, Psychologist

Everybody goes through periods of feeling down. But, depression is usually described as feeling persistently sad for weeks, months, or years. Major depressive disorder affects around 7% of the US population (17 million adults), and this is just one type of depression.

This page will cover what causes depression and signs of depression along with the different types and their subsequent treatments. If you are looking for the best places to start treatment today, check our best therapy sites for depression article. Skip to the very end of the article if you are looking at when to seek emergency help.

In this article, we will go through the root causes of depression.

Types of Depression

There are many depression causes and effects. Mental illness can often be a scale, and some may argue there are more categories than are commonly described. Furthermore, there are many reasons for depression and anxiety, so it’s important to look at identifying what type of depression it is first before treatment.

With that in mind, we have covered below the six most commonly described types of depression.

Major Depressive Disorder

If someone is feeling depressed most days of the week, the key disorder to check for is Major Depressive Disorder (MDD). For those wondering ‘is depression a mental illness?’, MDD is a good place to start when learning about how it can affect our lives.

This mood disorder is commonly diagnosed in individuals that have a low mood, lack of interest in their hobbies, changes in sleep, weight loss, and other symptoms for over two weeks. It’s seen by many as the ‘default’ depressive disorder.

Seasonal Affective Disorder

Seasonal Affective Disorder (SAD) deviates from major depressive disorder because it follows a seasonal pattern. Commonly known as “winter depression”, this is a mood disorder that derives from a lack of sunlight and vitamin D. The symptoms are similar to major depressive disorder, but the patient feels normal during the summer.

Psychotic Depression

Psychotic Depression happens when the depression comes from – or is paired with – psychosis. Psychosis is when someone loses touch with reality, such as having hallucinations, delusions, anxiety, and disorganized thoughts. This becomes more difficult to treat, as the psychosis needs to be treated as well as the depression.

Bipolar Disorder

Bipolar Disorder is a form of depression that describes drastic swings in mood, between mania (elevated mood) and depression. Bipolar is quite clear to identify because manic episodes are intensely euphoric, with the person having lots of energy and ambitious plans. Without this, the patient may just be diagnosed with MDD.


Dysthymia is a long-lasting type of depression, but is commonly defined to be milder. A Dysthymia diagnosis usually comes from when a patient has less severe symptoms than MDD, but they have had the symptoms for a long time, such as two years or more. With Dysthymia, you always feel down and apathetic, and you may even begin to think this is normal. 


With roots in the Hippocrates’ four personality types, melancholia is described to be a severe depression that often has physical symptoms, such as feeling sad, moving more slowly, and no longer enjoying activities that you used to. Often symptoms are worse in the mornings at the start of the day.

Most Common Causes For Depression

With many different types of depressive disorders, there are even more reasons and underlying causes for depression. Below are some major categories of depression causes and risk factors.

Biochemistry and Genetics

Many people consider depression as a chemical imbalance of the brain. Whilst this isn’t true for all forms of depression, biochemistry can play a big part.

When it comes to bipolar disorder, for example, a chemical imbalance is commonly the cause. Chemicals which are responsible for the brain functions such as serotonin and dopamine, can dramatically affect how we feel.

Major depressive disorder, among others, is also known to run in the family to some degree. Those with a parent or sibling with depression are at two to three times the risk regarding depression development. There could also be environmental factors being shared here, but most studies show depression and anxiety are moderately heritable.

Environmental Influence

With around 40% of depression cases being traced back to a genetic link, environmental factors (among others) account for the remaining 60%. And, when the average American has only one close friend along with $96,000 of debt, it’s clear how the stressful world we live in can easily generate higher levels of depression and anxiety.

This is even more noticeable when seeing trends across countries with varying levels of depression. Colder climates, for example, tend to have higher levels of depression due to SAD.


Personality also has relevance when looking at depression. Depression is proven to be linked with traits of neuroticism, being emotionally negative, conscientiousness, and other traits. Given that behavioral therapies are used to combat depression, it’s intuitive that behavior and personality are linked.

Trauma and Substance Abuse

A single traumatic event in life can have huge ramifications. Trauma is heavily linked to incarceration, substance use, interpersonal problems, aggression, and depression. Around 61% of men and 51% of women report having one or more traumatic events in their lifetimes, meaning the majority of the US population is at risk of these factors. For more on that, read our article about mental health statistics in the U.S.

Substance misuse is strongly linked to depressive disorders. Alcohol, for example, is a depressive drug in and of itself. Like many other substances, the ‘high’ comes at a cost, which is usually feeling depressed the next day. 

Depression Symptoms

Feeling sad is often described as being depressed. In truth, there are more symptoms than this, and sometimes, feelings of sadness are not overwhelming. Instead, it can be hard to detect, or you simply feel apathetic instead. Below is the full range of depression symptoms.

Psychological Symptoms

  • A constant low mood
  • Low self-esteem
  • Feeling helpless
  • No motivation 
  • Apathetic to activities you previously enjoyed
  • Anxiety 
  • Suicidal thoughts

Physical Symptoms

  • Losing weight
  • Decreased appetite 
  • Moving and talking slower than usual
  • Lack of energy
  • Loss of libido
  • Constipation
  • Disturbed sleep and insomnia

Finally, these symptoms can often manifest in other areas of life which could be more identifiable for some. For example, performing worse at work, no longer meeting up with friends, having relationship difficulties, and neglecting your hobbies can all be symptoms.

Symptoms in Children and Teens

Data suggests that depression can affect children as young as three. This is usually identified through extreme behavior that deviates from the norm, such as social interactions and emotional behavior.

Signs of early depression include being irritable, sad, angry, tired, and apathetic. However, sleeping more than usual (or not enough), difficulties concentrating, being indecisive, and feeling worthless.

If you suspect your child might be dealing with a mental health issue such as depression, anxiety or stress – there are plenty of excellent teen therapy services available online. That said, most of these only cater to kids aged 13 or above, so if your child is younger than that, a face to face consultation is the better route. 

Symptoms in Elderly People

Depression in elderly people can come from losing lifelong partners, loneliness, and illness – among the more common causes too. 

Symptoms in elderly people often revolve around feeling low, lonely, hopeless, irritable, as well as having a decrease in energy. Furthermore, it can cause memory and concentration problems worse too.

Being isolated and in constant fear for your health can easily become a trigger and so it is very important to be aware of and monitor your wellbeing constantly. Since depression and anxiety are known to cause physical problems and not just psychological ones, elderly people should not overlook this part of their health at all.

Depression with Anxiety

Depression and anxiety are very closely linked. Being the two most common psychiatric illnesses, they often come as a pair. When looking at depression causes and treatment, anxiety is often diagnosed and treated in similar ways too.

Around 60% of patients with anxiety also have symptoms of depression. The reasons behind this are far-reaching, as both are linked to substance abuse and other disorders, but they also impact one another. For example, regular panic attacks can cause a person to feel helpless, which is a symptom of depression.

For that reason, usually these two are treated together. CBT for example has been proven to be highly effective in treating both anxiety and depression. However, if you are looking specifically for help with anxiety, read our guide for the best anxiety treatments online

Depression with OCD

Obsessive Compulsive Disorder is often thought to be simply overly clean or superstitious. However, symptoms are a lot more varied than this, but are all rooted in obsessive thinking and behavior. Another way this can manifest, of course, is through negative obsessive thoughts about yourself. 

Depression, therefore, has some relationship to OCD. OCD “predicts depressive symptoms at two-year follow up and not vice versa. This relationship disappeared at four-year follow up,” according to one study.

Treating Mild Caes of Depression

Depression is a scale and recommended treatment correlates with that. For mild depression, temporary depression, and Dysthymia, it is common to begin with some self-help and doctor appointments. For example, eating more healthy food and exercising is a great first step. In conjunction with this, it’s commonly recommended to work on yourself, look for self-help groups, meditate, write a journal, and finally, seek out some counseling if needed.


Whilst a wide range of medicines and drugs have been tested to treat depression, the most commonly prescribed are antidepressants. These drugs tackle our brain chemistry by altering our neurotransmitters. There are a few types, but newer and highly common antidepressants include SSRIs and SNRIs. These same medicines are used to tackle OCD, anxiety, and PTSD, highlighting just how many disorders depression can overlap with.

However, antidepressants cannot change our personality, environment, past trauma, and other variables – they are strictly mood stabilizers. Antidepressants can also have side effects ranging from nausea, increased appetite, fatigue, insomnia, and negative sexual side effects, among others.

For that reason, it is usually recommended to combine these medications with a long term therapy plan.  If you are already on a prescription, you can get your medication for cheap and include a weekly therapy session through Brightside. Read our Brightside review and see if this is the holistic solution you might be looking for.

Online Cognitive Behavioural Therapy

Cognitive behavioral therapy (CBT) aims to tackle what antidepressants cannot – changes to our behavior and thought processes through specific techniques. 

CBT is often a course of 20 sessions or similar in which the licensed therapist will ask the patient to break their problems down into smaller parts. By identifying and changing a patient’s behavior and thought patterns, they can begin to break negative thought cycles.

CBT is profoundly effective in treating depression, and CBT delivered remotely is also shown to be just as effective as a traditional, face-to-face treatment. Our top picks for therapy sites for depression all offer extensive CBT treatment options at a very reasonable cost.

When to Seek Emergency Help

If you are experiencing a mental health crisis or severe depression, it is important to know that support is readily available. You don’t have to look at how to cure depression alone.

There are many signs of depression and it is advised to seek immediate treatment should you experience any. However, you do not need to wait for a doctor’s appointment during a crisis.

If you are experiencing suicidal thoughts, psychosis, or a crisis of despair, then it’s important to get help quickly

If a situation is potentially life-threatening, call 911 for emergency assistance.

If you or someone you know is in a crisis, in extreme emotional distress, or is suicidal, contact the 988 Suicide & Crisis Lifeline. You can call, text, or chat 988 and will be connected to a toll-free, confidential call with a trained worker.