Depression is a mental health condition that entails persistent feelings of sadness, apathy, hopelessness, loss of energy, and/or lack of interest in life.

Mild versions of these feelings are normal parts of day-to-day life. It's common, and even healthy, to feel sad or hopeless in reaction to stressful life events, the state of the world around you, or just to go through a period where things feel off.

But when these emotions become especially frequent, intense, or long-lasting, they can interfere with daily life activities.

Symptoms of depression

The severe symptoms of depression can vary and may sometimes seem to contradict each other. Common symptoms in men tend toward anger, irritability, and fatigue, while women's symptoms are more related to feelings of guilt, worthlessness and sadness. Likewise, there are some differences in symptoms between adults and children. Generally, some of the most common emotional and physical symptoms include:

• Persistent intense sadness or feelings of hopelessness: These feelings might occur without an obvious cause and may not improve when external circumstances improve.
• Lack of energy: Those struggling with depressed mood may find it difficult to get out of bed and complete daily activities.
• Irritability or restlessness: Some presentations of depression may include excessive or agitated activity, rather than (or alternating with) a lack of energy.
• Difficultly concentrating: You might feel a general sense of mental fogginess, and/or find it harder to focus and think things through.
• Loss of interest in pleasurable activities: Experiencing apathy is common when the things that usually bring you joy (social activities, hobbies, sex) may seem dull and uninteresting.
• Changes in sleeping or eating habits: Feelings of sadness and negative emotions can cause you to sleep or eat too much or too little, often resulting in rapid weight gain or significant weight loss.
• Thoughts of suicide or death: These feelings of worthlessness and negative thoughts may be persistent, involuntary, and disruptive to your daily life.

It is important to rule out other mental disorders or medical illnesses and diseases, like hypothyroid problems, diabetes, anemia or other chemical imbalance when looking for a diagnosis.

Different types of depression

Several different conditions fall under the umbrella of mood disorders. The diagnosis of depression comes from a medical health care provider after the completion of a physical and mental evaluation. With prolonged and severe symptoms, the most common forms are:

• Major Depressive Disorder: This is the most usual form of depression. Those struggling with major depression experience several of the above symptoms most days, to a degree that clearly affects their day-to-day lives. These symptoms persist for at least two weeks and are generally not related to specific life stressors (loss of a job, death of a loved one, etc.).
• Persistent Depressive Disorder: People with this form of depression experience milder versions of the same symptoms described above. These indications are still present most of the time, but they are less severe symptoms and those people struggling with chronic depression may be able to hide these symptoms from most people in their lives.
• Premenstrual Dysphoric Disorder: Also known as PMDD, this form of depression is an extension of PMS. Its occurrence is linked to a woman's menstrual cycle and usually involves the onset of depressive symptoms about seven to 10 days before the start of a menstrual period.
• Substance-Induced Depressive Disorder: Here, depressive symptoms are connected to the patient's substance use disorder or abuse of alcohol or other substances.
• Depressive Disorder due to Another Medical Condition: Certain medical conditions can cause depressive symptoms. In this type, the medical condition physiologically affects the individual's brain chemistry to cause the symptoms; it is not a psychological response to being sick.
• Seasonal Affective Disorder (SAD): Often equated to the 'winter blues,' SAD is a more severe with increased symptoms that can resemble those of Major Depressive Disorder. Typically triggered by a lack of sunlight or changes in seasons, SAD tends to occur during the winter months and is often treated with light therapy.

It is not uncommon for depressed people to also suffer from co-occurring disorders, like anxiety or bipolar disorder. A medical condition or physical illness like heart disease or cancer can sometimes be an underlying cause as feelings of hopelessness often are part of dealing with major illness.

It's important to understand that depression and anxiety disorders are not the same thing, even though they can share similar symptoms. Anxiety disorders have their own distinct causes and symptoms. Interestingly, many people who experience anxiety have also struggled with a history of depression, although there is no proven link between the two. It's clear, though, that both conditions can be challenging to manage and can greatly affect a person's well-being.

Bipolar disorder, formerly known as manic depression, is also a chronic mood disorder, with periods of low or depressed mood and/or major depression symptoms, but also includes periods of mania. Depression and bipolar disorder are serious mental disorders, though they present with different diagnostic criteria. Medical and mental health professionals have effective treatment plans for both.