Why Do People Get Depressed?

Depression is very common in teens. It affects people of every age, economic situation, and race.
So what causes it? Why do some people get depressed but others don't?

No One Reason for Depression

Lots of things play a role in whether a person gets depressed. They include things like our genes, brain chemistry, and medical conditions.
In addition to physical causes, there are other, more surprising things that can lead to depression. They include daylight and seasons, social environment, and life events. Why can these things play a part in someone getting depression? They can affect the brain's neurotransmitters (chemicals in the brain that regulate mood).
A person's outlook also can influence depression. Are you a glass-half-full or glass-half-empty kind of person? Do you get easily upset or do things roll off your back? The way that people think about (and react to) the events in their lives also can affect depression.
As if that's not confusing enough, sometimes there's just no obvious reason why some people get depressed. But their depression can still be very real and upsetting. Depression is a health condition that needs treatment, just like asthma or diabetes.

Genes

Research shows that depression runs in families. Some people inherit genes that make it more likely for them to get depressed.
Not everyone who has the genes for depression actually gets depressed, though. As with other health problems — like diabetes — just having the genes doesn't mean someone automatically gets sick. It just means there's a chance of it.
Many people who have no family history of depression still get depressed. So although genes are one factor, they aren't the only thing that can cause depression.

Brain Chemistry

Depression affects the brain's delicate chemistry. Here's how: Chemicals called neurotransmitters help send messages between nerve cells in the brain.
Some neurotransmitters regulate mood. When someone is depressed, these neurotransmitters might be in low supply or not in proper balance.
Genes and brain chemistry can be connected: People who have a genetic tendency to depression may be more likely to develop the imbalance of neurotransmitter activity that is part of depression.
Lots of things can affect the production and balance of neurotransmitters — including surprising things like stress and exposure to daylight. Using alcohol and drugs also can cause chemical changes in the brain that affect mood.
Medicines that doctors use to treat depression work by helping to restore the proper balance of neurotransmitters.

Seasons and Daylight

Daylight can affect how the brain produces some neurotransmitters, like melatonin and serotonin. When there is less daylight, the brain produces more melatonin. When there is more daylight, the brain produces more serotonin.
Melatonin and serotonin help regulate a person's sleep–wake cycles, energy, and mood. Shorter days and longer hours of darkness in fall and winter may cause increased levels of melatonin and decreased levels of serotonin. The change in balance can create the biological conditions for depression in some people who are sensitive to seasonal changes in daylight. This is known as seasonal affective disorder (SAD). Exposure to light can help improve mood for people affected by SAD.

Life Events

The death of a family member, friend, or pet can go beyond normal grief and sometimes lead to depression. Other difficult life events — such as when parents divorce, separate, or remarry — can trigger depression. Even events like moving or changing schools can be emotionally challenging enough that a person may become depressed.
Sometimes, though, a person may have depression without being able to point to any particular sad or stressful event. And many people go through difficult life events without becoming depressed.

Family and Social Environment

For some people, a negative, stressful, or unhappy family atmosphere can affect their self-esteem and lead to depression. Other high-stress living situations — such as poverty, homelessness, or violence (in a person's family, relationships, or community) — can contribute, too.
Dealing with bullying, harassment, or peer pressure can leave someone feeling isolated, victimized, or insecure. Situations like these don't necessarily lead to depression, but facing them without relief or support can make it easier to become depressed.

Health Conditions and Hormonal Changes

Certain health conditions change the balance of hormones in the body, affecting a person's mood. Some conditions, such as hypothyroidism, are known to cause a depressed mood in some people. When these health conditions are diagnosed and treated by a doctor, the depression usually disappears.
Because hormones affect mood, the normal hormonal changes that go along with puberty can make some people more vulnerable to depression.
For some people, health conditions may cause depression even though the condition itself doesn't physically change the body's hormones. For example, undiagnosed learning disabilities might block school success and lead someone to become depressed. Or illness might present challenges or setbacks that escalate into depression.
Whether or not these things lead to depression can depend a lot on how well a person is able to cope, stay positive, and receive support.

Reacting to Life Events

Life is full of ups and downs. Stress, hassles, and setbacks happen (but hopefully, not too often!). How we react to life's struggles matters a lot. A person's way of thinking can contribute to depression — or it can help guard against it.
Research shows that a positive outlook acts as a protection against depression, even for people who have the genes, brain chemistry, or life situations that put them at risk for developing it. The opposite is also true: People who tend to think more negatively can be more at risk for developing depression.
We can't control our genes, brain chemistry, or some of the other things that contribute to depression. But we do have control over how we see situations and how we cope.
Making an effort to think positively — like believing there's a way around any problem — can help ward off depression. So can developing coping skills and a support system of positive relationships. These things help build resilience (the quality that helps people bounce back and do well, even in difficult situations).
Here are three ways to build resilience:

1. Try thinking of change as a challenging and normal part of life. When a problem crops up, take action to solve it.
2. Tell yourself that setbacks and problems are temporary and solvable. Nothing lasts forever.
3. Build a support system. Ask friends and family for help (or just a shoulder to cry on) when you need it. Offer to help when they need it. This kind of give and take creates strong relationships that help people weather life's storms.

Being positive and resilient isn't a magic shield that automatically protects us from depression. But these qualities can help offset the other factors that might lead to trouble.

Source:  http://kidshealth.org/en/teens/why-depressed.html#