Major Depressive Disorder: Symptoms, Diagnosis, and the Weeks That Shape Treatment

Maybe you’ve felt flat for weeks. Your sleep is off, the things you used to enjoy feel like chores, and you keep telling yourself it’s just a rough patch. Or you already have a diagnosis and you’re wondering what’s supposed to happen next. It’s okay to not have all the answers right now.

Your brain is constantly tuning mood, sleep, appetite, energy, and motivation through networks of nerve cells that signal one another. In major depressive disorder, that tuning stays off for weeks at a time, and NIMH’s depression overview notes that genetic, biological, environmental, and psychological factors all play a role. Because those systems shift gradually, treatment works best with precision: knowing where you started, measuring how you respond, and adjusting on a schedule instead of by guesswork.

The standard treatments for depression rest on a deep evidence base. In a 2018 Lancet network meta-analysis of 522 trials with 116,477 adults, all 21 antidepressants studied worked better than placebo for major depression. Structured psychotherapy, especially cognitive behavioral therapy (CBT), has its own strong track record, and combining the two often works better still. The results are real, and the science is well established.

But starting treatment and checking back months later is no longer the best version of depression care, and at Siggy we’d rather build in the checkpoints that current guidelines recommend.

That approach is called measurement-based care, which means tracking symptoms with validated questionnaires at regular intervals so each treatment decision follows your actual response. It uses the same medications and therapies with more precision, because guidelines now spell out when early improvement should appear and when to change course. It also targets a well-documented gap, since many people stop treatment in the first month before it has had a fair chance to work. Checkpoints like these exist because of what the outcome data show about how depression responds over time.

What This Page Covers

• What Is Major Depressive Disorder?
• What Are the Symptoms of Major Depression?
• How Is Major Depressive Disorder Diagnosed?
• What Treatments Work for Major Depression?
• What Should the First Few Months of Treatment Look Like?
• How Siggy Fits In
• The Bottom Line on Major Depressive Disorder
• Start Your Anonymous Intake

What Is Major Depressive Disorder?

Major depressive disorder (MDD) is the clinical name for what most people call depression or clinical depression. NIMH draws the line this way: everyday sadness usually fades with time, while MDD can cause severe symptoms that change how you feel, think, and handle basics like sleeping, eating, and working.

It’s also common. In a nationally representative survey of 36,309 U.S. adults interviewed in 2012 and 2013, 10.4% had MDD in the past year and 20.6% had it at some point in their lives. The odds were higher among women, adults ages 18 to 29, and people with lower incomes, and most lifetime cases were moderate or severe. If this is happening to you, you’re far from alone.

What Are the Symptoms of Major Depression?

Clinicians look for a specific pattern rather than a single feeling. NIMH’s episode definition describes a period of at least two weeks with depressed mood or loss of interest, plus most of a set of specific symptoms involving sleep, eating, energy, concentration, or self-worth.

According to a StatPearls clinical review, a diagnosis requires at least five of nine core symptoms, with at least one being depressed mood or loss of interest, and they must cause problems at work or in your social life. Those nine symptoms fall into a few groups:

• Persistent low mood, or losing interest in things you used to enjoy
• Changes in appetite or sleep, in either direction
• Low energy, or feeling physically slowed down or restless
• Feelings of guilt or worthlessness
• Trouble concentrating or making decisions
• Thoughts of death or suicide

Depression doesn’t always look like sadness. The same review notes that people often first see a primary care doctor for physical complaints, and in almost half of cases they deny feeling depressed. Anxiety is also common alongside it: in the national survey above, 74.6% of people with MDD had prominent anxious distress. Children and teens may come across as irritable rather than sad.

If you’re having thoughts of suicide or self-harm, call or text 988 to reach the Suicide and Crisis Lifeline, or call 911 if you’re in immediate danger.

How Is Major Depressive Disorder Diagnosed?

MDD is a clinical diagnosis, so there’s no scan or single blood test that confirms it. A clinician takes your history, including medical, family, social, and substance use history, and assesses your mood, thinking, and concentration. The StatPearls review describes routine lab work, such as a blood count, metabolic panel, thyroid tests, vitamin D, urinalysis, and a toxicology screen, to rule out medical causes.

That step matters because several conditions can mimic depression. Thyroid disorders, vitamin B12 or D deficiency, neurological illnesses, and some medications, including steroids and certain blood pressure drugs, can all produce depressive symptoms.

Questionnaires help put numbers to what you’re feeling. The PHQ-9 scores each of the nine core symptoms from 0 to 3. In its original validation study in primary care and OB-GYN clinics, a score of 10 or higher matched a mental health professional’s structured interview with 88% sensitivity and 88% specificity for major depression. Scores of 5, 10, 15, and 20 mark mild, moderate, moderately severe, and severe depression. It’s useful for screening and for tracking change, but it can’t make a diagnosis by itself.

A careful evaluation also asks whether you’ve ever had mania or hypomania, meaning stretches of unusually high energy, little need for sleep, or racing thoughts. A history like that points toward bipolar disorder, which is treated differently.

What Treatments Work for Major Depression?

Several treatments have strong evidence, and the right choice depends on severity, your history, and what you prefer. A 2020 network meta-analysis of 101 trials with 11,910 patients found that medication alone and psychotherapy alone performed about the same, while combining them was more effective than either one. People were also more likely to stick with combined treatment or therapy than with medication alone.

Here’s how the main evidence-based options compare at a glance.

Treatment	What the Evidence Shows	Good to Know
Antidepressant	All 21 studied beat placebo	Progress checked at 2 to 4 weeks
Psychotherapy (CBT)	About as effective as medication	Benefits may hold longer after treatment
Combined	Better response than either alone	Often preferred for moderate depression
Exercise	Moderate symptom reduction	Evidence certainty is limited

The CANMAT 2023 guidelines note that antidepressants may work slightly better on some symptoms in the short term, while CBT outperforms antidepressants at 6 to 12 months of follow-up. For exercise, a 2024 BMJ meta-analysis of 218 trials found moderate reductions in depression with walking or jogging, yoga, and strength training, with bigger effects at higher intensity. The authors rated their confidence in the evidence as low to very low, so exercise works best as part of a plan rather than a replacement for one.

For severe depression or depression that hasn’t responded to several treatments, options like transcranial magnetic stimulation (TMS), esketamine, and electroconvulsive therapy (ECT) are available. Our guide to treatment-resistant depression explains when those come into play.

What Should the First Few Months of Treatment Look Like?

Antidepressants take time, so the early weeks are about watching for the first signs of change. CANMAT defines early improvement as a drop of 20% or more on a symptom scale within 2 to 4 weeks. If that hasn’t happened by about 4 weeks, the guideline says the chance of response or remission at 8 to 12 weeks is low, and the next step is to raise the dose or switch medications. It also recommends repeating symptom scales every 2 to 4 weeks while those decisions are being made.

That timeline only helps if someone is actually watching. A common frustration in depression care is that no one checks in to see if it’s actually working, and the data back that up. In a U.S. continuity study, 42.4% of adults starting an antidepressant for depression stopped within the first 30 days, and only 27.6% continued past 90 days. People who were also in psychotherapy were more likely to stay on treatment past the first month, at 68.0% compared with 43.7%.

Feeling better is the goal, but it’s also the moment people are most tempted to stop. CANMAT recommends continuing an antidepressant for 6 to 12 months after remission, and longer for people with risk factors for recurrence. A 2003 Lancet review of 31 trials with 4,410 participants found that continuing treatment cut the odds of relapse by 70%. Relapse happened in 41% of people switched to placebo compared with 18% of those who stayed on medication.

When it is time to stop, plan the taper with your prescriber instead of quitting on your own. For a week-by-week view of what to expect early on, see our guide to how long antidepressants take to work.

How Siggy Fits In

Siggy’s licensed prescribers diagnose and treat the full range of mental health conditions, including major depressive disorder. Siggy’s intake gathers structured information and doesn’t diagnose you on its own. A licensed prescriber reviews your full intake, including your symptoms, history, other medications, and anything that could point to a different diagnosis, before anything is prescribed.

The anonymous intake asks for no name, email, or account, so you can describe what’s really going on, like how long it’s lasted or what hasn’t worked before, without worrying how it sounds. You’ll get a downloadable summary to keep or share with any clinician. If you’re already being treated for depression, keep working with the clinician who manages it, and bring your summary along.

Siggy isn’t an emergency service. If you’re in crisis, call 911 or call or text 988. This article is for education only and isn’t a substitute for personal medical advice. It reflects sources available as of October 2026.

The Bottom Line on Major Depressive Disorder

Major depressive disorder is common, diagnosable, and treatable. A good evaluation rules out medical causes and bipolar disorder, and the strongest treatments, medication, psychotherapy, or both, work best when progress is measured early and treatment continues well past the first good week. If you’re curious about the biology and life events behind it, our explainer on what causes depression goes deeper.

Start Your Anonymous Intake

If you’re in crisis right now, call 911 or call or text 988 first. If low mood has been weighing on you for weeks and you want help figuring out what comes next, start your anonymous intake. It’s free, there’s no name or email required, and a licensed prescriber reviews your intake before anything is prescribed. Your summary is yours to keep and share with whoever helps you next.