Medically reviewed by Angela Sheddan, FNP
Written by Our Editorial Team
Last updated 3/22/2022
Bipolar disorder and major depressive disorder (MDD) are two common forms of mental illness that can affect children, adolescents and adults.
According to data from the National Comorbidity Survey (NSC), an estimated 4.4 percent of all US adults experience bipolar disorder at some point in life. Depression is even more common, with an estimated 8.4 percent of all adults affected at some point in 2020, respectively.
Bipolar disorder and major depression can both produce similar symptoms. However, there are also several key differences between these two common disorders, including the most effective forms of treatment for each.
Below, we’ve explained what bipolar disorder and depression are, as well as the symptoms you may develop from each type of mental illness.
We’ve also explained how you can tell the difference between bipolar disorder and depression, as well as the steps that you can take to receive expert help if you think you may have a mood disorder or other mental health problem.
Bipolar disorder (previously referred to as manic-depressive disorder or manic depression) is a mental disorder that involves dramatic, abrupt changes in your moods, energy levels and daily function.
Although it’s normal to experience good and bad days, people with bipolar disorder often have very severe symptoms that far exceed normal mood swings or changes in energy levels.
Bipolar disorder can affect people of all ages, but it’s most common in young adults, with rates declining from 4.7 percent in people aged 18 to 29 to 0.7 percent in people 60 and older.
People with bipolar disorder typically have severe, recognizable changes in mood, energy and activity that are referred to as “mood episodes.”
Bipolar disorder may involve periods of significant elation, irritability and high levels of physical activity referred to as manic episodes. It may also involve periods of sadness, emptiness and a lack of activity referred to as depressive episodes.
If you have bipolar disorder, you may experience these changes in your thoughts, feelings and behavior, often without recognizing the impact they can have on your life and wellbeing.
During a manic episode of bipolar disorder, it’s common to:
Feel ecstatically happy or satisfied
Become irritable and oversensitive
Have a general feeling that you’re “wired”
Talk rapidly about many different topics
Feel as if you can do many things at the same time
Perceive yourself as powerful, important or extremely capable
Lose your appetite and stop eating
Feel like you don’t need to sleep
Spend money excessively or generously give to others
Engage in other risky, reckless behaviors
During a depressive episode, it’s common to:
Feel worried, hopeless or extremely sad
Find it difficult to fall asleep or stay asleep
Sleep too much and struggle to wake up
Feel as if you’re thinking and moving slower than usual
Talk slowly and feel like there’s nothing for you to talk about
Feel as if you’re unable to do anything, even simple tasks
Perceive yourself as worthless or helpless
Constantly feel hungry and eat more than usual
Lose your interest in satisfying activities, including sex
Experience thoughts of death or suicidal ideation
Experts have identified three different types of bipolar disorder:
Bipolar I disorder. This type of bipolar disorder involves manic episodes that persist for seven days or longer or severe manic symptoms that require hospitalization. It can also involve depressive episodes that may last for two weeks or longer. Some people with bipolar I disorder develop episodes of depression with mixed features (an episode of depression that also involves symptoms of mania).
Bipolar II disorder. This type of bipolar disorder involves a mix of depressive episodes and hypomanic episodes (episodes of mania that are less severe than those in people with bipolar I disorder).
Cyclothymia. This is a rare mood disorder that involves a mix of periods of hypomanic symptoms and depressive symptoms that persist for at least two years. The symptoms of cyclothymia are less extreme than those of other types of bipolar disorder.
Not everyone with bipolar disorder fits clearly into one of the above categories. When a person has a mix of symptoms that do not match the above categories, they may be defined as having “other specified and unspecified bipolar and related disorders.”
The defining symptom of depression is a persistent sad, empty or anxious mood that occurs on a daily or near-daily basis. Other symptoms of depression include:
A reduced level of interest in your hobbies, passions and other activities
Feeling as if you’re guilty of something, worthless or unable to be helped
Irritability and a “shorter fuse” when dealing with other people
A hopeless and overly pessimistic attitude towards your life
Difficulty falling asleep, staying asleep or waking up at a normal time
Decreased energy levels and a general sense of physical fatigue
Difficulty focusing on tasks, making decisions or remembering things
Changes in your appetite, eating habits and/or bodyweight
Physical aches, pains, cramps and digestive issues without an obvious cause
Slowed physical movements and/or speech patterns
Difficulty staying still and a general feeling of physical restlessness
Thoughts involving death, or suicidal thoughts and/or behavior
These symptoms may vary in severity. In order to be diagnosed with depression, you’ll generally need to have several symptoms — in addition to a poor mood — that occur either daily or almost daily over a period of at least two weeks.
In addition to major depressive disorder, there are several other forms of depression, each with different symptoms or characteristics:
Seasonal affective disorder. This is a seasonal depressive illness that can develop in winter as a result of changes in sunlight levels. It often improves as sunlight increases during spring and summer.
Persistent depressive disorder. This is a long-lasting form of depression that occurs for two years or longer, often with symptoms that vary in intensity. It’s often referred to as dysthymia.
Atypical depression. This is a form of depression that involves atypical features, such as mood reactivity (the ability for a person’s mood to improve in certain situations).
Psychotic depression. This is a severe form of depression that involves symptoms of psychosis, such as hallucinations and delusions. Treatment for this form of depression may involve hospitalization.
Our detailed guide to the types of depression provides more information about how these forms of depressive illness differ in terms of symptoms, severity and treatment.
Bipolar disorder and depression have numerous similarities, as both are mood disorders that involve depressive symptoms.
The key difference is that bipolar disorder involves manic episodes and depressive episodes, resulting in distinct periods that involve very different moods, thoughts and behavior.
Depression, on the other hand, is defined purely by depressive symptoms, without the manic episodes that can occur with bipolar disorder.
This is where the names of these two mood disorders come from. The prefix “bi” means two, and “bipolar” disorder is a disorder that involves two distinct poles, or extremes — mania and depression.
Major depressive disorder is sometimes referred to as “unipolar” disorder for the same basic reason — it only involves a single pole, or extreme, which is depression.
If you have bipolar disorder, you may experience sudden, significant changes in your moods, thoughts and energy levels from manic to depressive. These changes can occur over weeks and have a severe impact on your health, quality of life and ability to function.
If you have major depressive disorder, you may experience persistent and severe depressive symptoms. These symptoms may occur on a daily basis. However, you won’t switch between periods of depression and mania.
Bipolar disorder and major depressive disorder are both treatable. To diagnose bipolar disorder, your healthcare provider may carry out a physical exam and a mental health evaluation to learn more about your symptoms.
If appropriate, you may receive a mental health referral. Your mental health provider may talk to you about your symptoms and overall mental wellbeing. You may be asked about your personal or family history of bipolar disorder or other forms of mental illness.
You can also seek treatment from home with our online psychiatry service, which allows you to connect with a licensed psychiatry provider online for an evaluation.
Although there’s no way to cure bipolar disorder, it can usually be treated with a combination of medication and psychotherapy.
The most common medications for treating bipolar disorder are mood stabilizers and atypical, or second-generation, antipsychotics. These medications work by preventing highs and lows that can occur with bipolar disorder and stopping delusions, hallucinations and paranoid thoughts.
In some cases, antidepressants (medications that control your levels of natural chemicals called neurotransmitters) are also used to treat bipolar depression.
If you’re prescribed medication to treat bipolar disorder, make sure to use it exactly as instructed by your healthcare provider. Inform your healthcare provider if you develop any side effects from your medication.
Several forms of psychotherapy, or talk therapy, are used to treat bipolar disorder. These include cognitive behavioral therapy (CBT), psychoeducation and more recent forms of therapy such as family-focused therapy and interpersonal and social rhythm therapy (IPSRT).
In some cases, other forms of treatment, such as electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS) may help to improve bipolar disorder.
Most forms of depression are also treated with a combination of medication, psychotherapy and lifestyle changes.
The most common medications for treating depression are antidepressants. These medications work by increasing the levels of certain neurotransmitters that control your moods, feelings and levels of stress.
Your mental health provider may prescribe a type of antidepressant called a selective serotonin reuptake inhibitor (SSRI) to improve your moods and other symptoms. In some cases, you may need to use another type of antidepressant to improve your symptoms and quality of life.
Antidepressants are effective, but they can take several weeks to start working. You may notice that your mental focus, sleep and other symptoms improve before you notice any improvements in your moods and behavior.
Make sure to use your medication exactly as prescribed by your mental health provider. If you’re prescribed an antidepressant, do not reduce your dosage or stop taking your medication without first talking to your mental health provider.
Depression often improves with psychotherapy. Common forms of psychotherapy for depression include cognitive behavioral therapy, problem-solving therapy and interpersonal therapy (IPT).
Like bipolar disorder, severe or persistent depression may also be treated with electroconvulsive therapy and other brain stimulation therapies.
Bipolar disorder and clinical depression can both cause you to feel unhappy, drained of energy and dissatisfied with life. However, while major depression only involves depressive symptoms, bipolar disorder involves both depressive symptoms and symptoms of mania.
If you’ve noticed depression or bipolar symptoms, it’s important to talk to a licensed healthcare provider about your concerns.
You can do this by talking to your primary care provider, consulting a psychiatrist locally or from your home using our online mental health services.
Bipolar disorder and depression can both be treated. By seeking help, you can get control over your thoughts, feelings and moods, allowing you to manage your symptoms and enjoy a higher quality of life.