We all feel sad sometimes. But if you’ve been feeling very low for more than two weeks, you may be experiencing depression.

Sadness, anger, and tiredness are all natural human emotions. We’re usually able to manage these feelings, and they don’t tend to get in the way of our lives too much.

Depression, on the other hand, is a serious condition that affects your mental and physical health. It affects your mood, how you see yourself, and even your eating and sleeping habits.

Depression is a mental health condition that lasts two weeks or more in which you feel sad, emotionally sensitive, hopeless, or uninterested in things that you usually love.

The good news is that depression is treatable, and help is available. Lots of treatments can help, including therapy, self-care, and in some cases, antidepressants.

Depression is a widespread mental health disorder. So if you have it, you’re definitely not alone.

In fact, depression is one of the leading causes of disability in the United States and worldwide. It affects around 264 million people globally and 17.3 million adults in the United States.

Other names for depression include major depressive disorder, major depression, and clinical depression.

We all feel sad or lonely from time to time. That’s part of being human.

But if you feel low or hopeless often — like almost daily — it might be depression. This is especially true if you’ve been experiencing symptoms for 2 weeks or longer.

You might not know what’s causing these lingering symptoms. You might not even know when they began. All you know is that you just haven’t felt like yourself in a while.

“Depression is something that doesn’t have much to do with outside circumstances,” says Rachelle Heinemann, a licensed mental health counselor in Brooklyn, New York. “There doesn’t seem to be a reason for it.”

In other cases, depression has an identifiable cause. A stressful life event, such as a sudden loss or a relationship change, might trigger low moods.

If these moods last a long time or are relatively severe, this might be considered depression, especially in someone who has a history of depressive episodes.

The loss of a loved one, or even the ending of a relationship, can lead to deep feelings of sadness or grief, but those feelings aren’t the same as having depression.

The grieving process tends to go in waves: Some moments, you might have positive memories or feel OK. Other times, you’ll feel down or lose interest in things you once loved. You also don’t usually suffer from low self-esteem or self-loathing during grief — but those are common symptoms of depression.

However, grief can lead to complicated grief or depression, especially if you find it difficult to move on from the loss.

Want to learn more? You can read about the stages of grief and mourning here.

Yes. Depression isn’t a one-size-fits-all.

“Many people with depression don’t even know they have it,” says Adrienne Meier, a clinical psychologist and telehealth practitioner. “Symptoms are often misattributed to fatigue or stress or even just ‘getting older.'”

These are different kinds of depression:

  • Persistent depressive disorder (Dysthymia): This condition is not as intense, but it drags on for two years or longer.
  • Depressive psychosis: This is a combination of severe depression and delusions or hallucinations.
  • Bipolar disorder: You alternate between periods of high energy and risky behavior (mania) and severe depression in which you find it difficult to cope.
  • Atypical depression: You might feel better for short periods in response to positive events. It can start earlier in life and last a long time.
  • Premenstrual dysphoric disorder (PMDD): This condition causes severe irritability, depression, or anxiety during the time between ovulation and your period.
  • Seasonal affective disorder: Most common in winter or regions where the days are particularly short in fall and winter. It’s believed to be caused by changes in circadian rhythms, serotonin, and melatonin in response to reduced light exposure.
  • Situational depression (or adjustment disorder): Begins with a stressful life event, such as a death, move, or family change. It usually begins within 3 months of the event and tends to resolve within 6 months.
  • Postpartum depression: Occurs during pregnancy or within 12 months of giving birth. It usually coincides with the hormonal and physical changes that come with parenthood.
  • Major depression: Also known as clinical depression, this is the most common kind of depression (and the focus of this article).

Major depression can cause a range of symptoms that last 2 weeks or longer.

Depression appears differently for each person, and its symptoms are not always consistent or clear-cut. You don’t need to experience all of the following to receive a diagnosis of depression, but it usually involves a combination of these symptoms:

Persistent feelings of sadness or hopelessness

“[Depression] feels deeper than sadness,” Heinemann says.

You might find yourself wondering what’s the point of getting up, or you might cry more easily.

Some people with depression say that it feels as if they’ve sunk into a deep, dark hole with no way out, and they have little to no hope that things will ever change.

Others feel worthless or guilty. You might find yourself dwelling on things you wish you could have done differently.

Or, you might not like yourself much right now. Self-loathing is a frequent symptom.

You’re less interested in things you usually enjoy

“Someone struggling [with depression] might lose interest in doing the things they used to be passionate about,” Heinemann says.

For example, if you used to lovegoing for walks, playing sports, or painting, but now you dread the idea of doing any of those things, that’s a big red flag for depression.

Depression can also impact your desire for sex, according to research.

You find it hard to concentrate, get things done, or take care of yourself

“Often those suffering from depression describe it as a weight on top of them, suffocating them, making it impossible to get out of bed or take care of their basic needs,” says Heinemann. “They feel drowned by depression.”

This can feel like being really low on energy.

“Some people find it difficult to do things like showering or brushing their teeth,” she says.

Others struggle with simple chores or concentrating at work. Even making decisions can feel difficult if you have depression.

“Depression tends to hijack our brain, so the strategies we usually use or rely on [to get things done] aren’t helpful because our brains are lying to us,” explains Meier. “We are seeing the world through poop-covered glasses.”

You feel irritable

Research suggests that irritability is a symptom that’s most common in males, but it can affect anyone. Irritability and aggression are also common signs of depression in children.

So if you find yourself prone to anger, aggressiveness, or feel as if everyone around you is irritating, this could signal depression.

Your sleep patterns have changed

You might feel tired all the time and find yourself sleeping a lot more than usual. Or you might find it difficult to sleep even when you’re tired, so you spend long nights awake in bed.

But research suggests that most people experience some sleep disturbance when they have depression.

Your appetite has changed

As with sleep, depression affects people’s appetites differently. Some people are hungry or feel the urge to eat all the time. Others don’t feel like eating at all.

Changes in your appetite can affect your weight, too — and quickly. For example, the Diagnostic and Statistical Manual for Mental Disorders (DSM-5) says that depression can lead to weight gain or loss of more than 5% of your body weight in a month.

You feel anxious

Depression doesn’t really cause anxiety, but a lot of people experience both conditions at the same time. So you might feel nervous, restless, or worried a lot. Your heart rate or breathing might change when you start to worry, or you might feel twitchy.

Feeling anxious? Here are 9 ways that can help to relieve anxiety right away.

Your body aches

For some people, depression causes physical symptoms like aches, pains and lots of headaches or migraines. Other people might be more sensitive to pain than usual.

For example, one study found that some people with mental health disorders — including major depression — had migraine attacks that preceded them.

You think about self-harm or suicide

This is the most serious symptom of depression — even if your thoughts of death or suicide are fleeting and don’t involve plans to follow through.

Some people have death ideation, which means feeling as if you don’t want to be alive anymore but don’t intend or have thoughts about self-harm or suicide.

If you or someone you know is considering suicide, you’re not alone. Help is available right now:

Not in the United States? Find a helpline in your country with Befrienders Worldwide.

Sometimes, people become depressed due to difficulties coping with many things over a period of time. Many find that work stress, relationship problems, and other issues accumulate over time.

Life events or major life changes, like moving away, can also cause depression and related conditions.

Feeling a lack of meaning or purpose can be one of the most common causes of depression, especially when you lose contact with activities that provide a sense of meaning, purpose, or sense of self.

A number of things that can cause or contribute to depression, including:

  • Brain structure: Research suggests that the hippocampus is smaller in some people with depression. A less active frontal lobe could also cause it.
  • Biochemistry: Differences in certain brain chemicals could contribute to depression.
  • Family history: You are more likely to have depression if depression or another mental health condition runs in your family.
  • Trauma: Stressful or traumatic events can impact how your body reacts to fear and stress in the future, which raises your risk of depression. This is especially true for childhood trauma.
  • Medical conditions: Chronic illness or pain, insomnia, and attention-deficit hyperactivity disorder (ADHD) are some of the conditions that could put you at a higher risk of developing depression.
  • Environmental factors: Exposure to abuse, violence, poverty, or trauma could make you more vulnerable to depression.

If you are noticing the symptoms of depression, a healthcare professional can help get you a diagnosis.

This will likely begin with a conversation and a physical examination. Your doctor will likely ask you about your family history to see if depression or other mental health conditions run in your family.

If you’re talking with your primary physician, they might also order blood tests to ensure that another medical condition isn’t the cause of your symptoms. For example, the fatigue or lethargy you can feel with depression could also be caused by vitamin deficiencies or a thyroid issue.

If your doctor can’t find another cause for your symptoms, they will likely refer you to a licensed mental health expert who will evaluate your mood, behavior, and day-to-day activities.

They will also ask you about your family’s psychological history. They may use a depression-rating questionnaire, such as the Hamilton Depression Rating Scale or the Patient Health Questionnaire 9 (PHQ-9), to diagnose the condition.

According to the DSM-5, you have to display at least five of the main symptoms of depression for over two weeks to get a diagnosis.

If you are experiencing symptoms of depression, it’s always best to talk with a healthcare professional, especially since some symptoms can be caused by underlying medical conditions rather than depression. The sooner you talk with them, the sooner you can get the help you need to start feeling better.

It’s OK if you’re feeling reluctant to talk to a mental health expert or doctor, but you have nothing to be ashamed of. It’s OK to ask for help. If you’re not comfortable sharing, then no one except you and your doctor has to know that you’re seeking treatment.

“We go to a doctor when our body isn’t feeling well, and we go to a therapist when our emotions feel out of whack,” says Heinemann. “Depression is not your fault, nor is it something you can just snap out of.”

Once you receive a diagnosis of depression, your mental health professional will discuss possible treatments for depression with you, including one or a combination of the following:

  • Antidepressants: These can help you begin to see improvement in your symptoms within a few weeks, though it could be a couple of months before you truly begin to feel better.
  • Psychotherapy: Better known as talk therapy, psychotherapy can help you learn to problem-solve and recognize negative thinking. Your therapist can also help you maximize meaningful behaviors and activities during your week. This helps many people cope with challenges in a more adaptive way.
  • Electroconvulsive therapy (ECT): This is reserved for people with the most severe kinds of depression who haven’t responded to other treatments. This is a safe and effective treatment.

Feeling better will be a process: It won’t happen overnight. But with time, you’ll notice an improvement in the way that you feel.