Everyone feels down now and then, but when sadness lingers for weeks and affects daily life, it may be more than just a mood swing.
This condition is known as Major Depressive Disorder (MDD), or clinical depression. It’s one of the most common mental health conditions worldwide, affecting more than 8% (21 million) of American adults each year.
In this guide, we’ll break down what MDD is, how it shows up across different ages, what causes it, and the treatments that can help.
What Is Major Depressive Disorder (Clinical Depression)?
Major depressive disorder (MDD) is a serious medical condition that affects how a person feels, thinks, and functions. To be diagnosed, symptoms such as persistent sadness, low energy, and loss of interest in daily activities must last for at least two weeks.
Doctors use set criteria to identify MDD, as it’s not just about “feeling sad.” It also involves changes in sleep, appetite, and concentration. In some people, it may even cause physical pain without a clear medical reason.
MDD also has several recognized subtypes. For instance, seasonal affective disorder (seasonal depression) usually occurs during winter months, while postpartum depression and prenatal depression are associated with childbirth.
There are also forms like atypical depression, where symptoms can temporarily lift in response to positive events.
In addition to MDD, there are several other distinct depressive disorders, including:
- Persistent Depressive Disorder (formerly known as dysthymia)
- Depressive disorder due to another medical condition
- Substance/medication-induced depressive disorder
- Disruptive mood dysregulation disorder
- Premenstrual dysphoric disorder
- Unspecified depressive disorder
While these variations exist, the common thread is that depression can deeply interfere with a person’s daily life, regardless of its specific form
Symptoms of Major Depressive Disorder
The common signs of clinical depression can look like:
- Fatigue and low energy
- Changes in appetite or weight
- Thoughts of self-harm or suicide
- Persistent sadness or emptiness
- Feelings of guilt or worthlessness
- Difficulty sleeping or oversleeping
- Loss of interest in hobbies and activities
- Trouble concentrating or making decisions
However, these symptoms are not the same for everyone. They can depend on a person’s age, health, and life stage.
Depression Symptoms in Children and Teens
In younger people, depression may not look like constant sadness. Children may become irritable, clingy, or have sudden changes in school performance. Teens may withdraw from friends, lose motivation, or show risky behavior.
Parents and teachers sometimes mistake these changes as “just part of growing up.” However, untreated depression in young people can carry into adulthood, making early support critical.
As kids grow older, these symptoms may shift again. That’s why it’s important to also look at how depression affects older adults.
Depression Symptoms in Older Adults
Depression in older adults often looks different from how it appears in children and younger adults. Fatigue, slowed thinking, difficulty sleeping, or memory problems are common and sometimes mistaken for normal aging or dementia.
Older adults may also pull back from social life, lose interest in hobbies, or show changes in appetite. Because these symptoms can overlap with other health conditions, depression may be overlooked.
When recognized and treated, older adults often respond well to therapy and medication. But what actually causes major depressive disorder in the first place? Let’s explore.
What Are the Causes of Major Depressive Disorder?
There isn’t one single cause of MDD. Instead, it usually develops from a mix of biological, genetic, and environmental factors.
Biological
Research shows that neurotransmitters like serotonin and dopamine, which regulate mood, may not work properly in people with MDD. Brain imaging studies have also found changes in certain circuits that affect emotion regulation.
Genetic
If a parent or sibling has depression, a person may face a higher risk. However, family history doesn’t mean someone is destined to develop it.
Psychological & Environmental
Life events often interact with these risks. Trauma, financial stress, relationship challenges, or long-term illness can trigger depression.
Because the causes are so complex, proper diagnosis is essential.
What Is the Main Difference Between Major Depressive Disorder and Bipolar Disorder?
On the surface, major depressive disorder and bipolar disorder can look alike. Both involve periods of sadness, low energy, and loss of interest in daily life.
The key difference is that bipolar disorder also includes episodes of mania or hypomania. During these times, a person may feel unusually energetic, need little sleep, or act impulsively.
This distinction matters because treatment is not the same. Medications used for MDD, such as antidepressants, may trigger manic episodes in someone with bipolar disorder. That’s why doctors carefully evaluate symptoms and history before confirming a diagnosis.
Once a diagnosis is clear, treatment options for major depressive disorder can be explored.
How is Major Depressive Disorder Treated?
Treatment for MDD often combines therapy, medication, and lifestyle support. No single method works for everyone, so care plans are usually tailored to the individual.
Cognitive Behavioral Therapy for Depression
One of the most effective therapies is cognitive behavioral therapy (CBT). CBT helps people identify negative thought patterns and replace them with healthier ones.
For example, instead of thinking “I always fail,” a person learns to reframe it into “I didn’t succeed this time, but I can try again.”
Studies show CBT can reduce relapse rates when combined with medication. It gives people practical tools they can use in daily life.
Other Treatments for Major Depressive Disorder
Medications are often used as a first-line treatment. These include SSRIs and SNRIs, which help balance brain chemicals linked to mood. For some, psychotherapy alone may be enough, while others need a combination of both.
In treatment-resistant cases, options like electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), or ketamine infusions may help. Lifestyle changes such as exercise, sleep routines, and nutrition support can also make a difference.
Does Depression Get Worse with Age?
No, depression does not always worsen with age. However, the way it presents can change.
Older adults may have more physical illnesses, social losses, or functional limitations, which can increase risk. But research also shows that many seniors report stable or even improved emotional well-being as they age, especially with treatment.
So, while age can shape how depression looks, it doesn’t mean things will get worse. Instead, with the right care, people can manage symptoms at any stage of life.
Is Major Depressive Disorder a Disability?
Major depressive disorder can sometimes qualify as a disability, depending on how much it limits daily functioning. In many countries, disability programs recognize MDD when symptoms interfere with work or self-care.
This doesn’t mean everyone with depression has a disability. Some people experience shorter episodes that respond well to treatment. But for others, the condition is long-lasting and requires ongoing support.
Join a Major Depressive Disorder Study
At Hightower, we’re committed to advancing care through research. Our MDD clinical trials study new treatments, therapies, and approaches that may not yet be widely available.
By joining a major depressive disorder study, participants contribute to scientific progress while gaining access to new care options. Every study follows strict safety guidelines and is overseen by medical professionals.
If you’re curious, you can explore our ongoing trials and see whether participation is right for you.
Taking the Next Step
Major depressive disorder is challenging, but it’s also treatable. With therapy, medication, and support, many people recover and lead fulfilling lives.
If you or someone you love is struggling, reaching out to a provider is a powerful first step. And if you’re interested in contributing to future treatments, consider learning more about Hightower’s MDD clinical trials.
You don’t have to face MDD alone. Support, care, and research are here to help guide the way forward.
