“Is this just a rough patch, or is it depression?” It’s one of the most common questions people quietly ask themselves — often for months before they say it out loud. The honest answer is that depression isn’t something you can diagnose from an article or an online quiz. It’s diagnosed by a trained professional. And far from being discouraging, that’s the reassuring part: you don’t have to work out the answer alone.
The quick answer: Depression is diagnosed by a qualified mental health professional through a careful conversation about your symptoms, how long they’ve lasted, and how much they’re affecting your life — guided by established clinical criteria. A doctor may also run tests to rule out physical causes that can mimic depression, such as a thyroid problem. Online quizzes can raise awareness, but they can’t diagnose you. If something feels persistently wrong, that’s reason enough to seek an assessment.
Depression is more than sadness
Part of why depression goes unrecognised is that people expect it to look like constant crying or obvious sadness. Often it doesn’t. It can show up as a flatness or emptiness, a loss of interest in things you used to enjoy, irritability, exhaustion, trouble concentrating, or changes in sleep and appetite — carried quietly while someone keeps going through the motions. What sets it apart from an ordinary low patch is that it persists, most of the day, for weeks, and starts to weigh on everyday life. (For more on the condition itself, see our guide to recognising depression.)
How depression is actually diagnosed
There’s no blood test or scan that detects depression directly. Instead, a mental health professional makes the diagnosis through clinical assessment — and there’s more rigour to it than people often imagine. Broadly, it involves:
- A clinical conversation. The heart of it. A psychologist or psychiatrist asks about your mood, thoughts, sleep, appetite, energy and concentration — how long things have been this way, and how much they’re affecting your work, relationships and daily life.
- Established diagnostic criteria. Professionals work to a recognised framework. Under the widely used DSM-5 criteria, a diagnosis of depression generally requires several specific symptoms to be present most of the day, nearly every day, for at least two weeks — with at least one being low mood or a loss of interest or pleasure — and to represent a real change from how you usually are.
- Screening questionnaires, sometimes. A brief questionnaire (such as the PHQ-9) may be used to gauge severity and track change over time. It’s a helpful aid — but it supports the professional’s judgement rather than replacing it. A score alone is not a diagnosis.
- Ruling out physical causes. A doctor may run tests, because several physical conditions — an underactive thyroid, for instance — can produce symptoms that look a lot like depression. Treating the wrong thing helps no one, so getting this right matters.
Why you can’t (and shouldn’t) self-diagnose
Online checklists and quizzes have their place — they can nudge someone toward realising they need help. But they can’t diagnose depression, for good reasons. The symptoms overlap with several other things: grief, burnout, anxiety, a thyroid condition, or the lows of bipolar disorder, which look similar but need very different care. Telling these apart takes clinical training and a proper conversation. The risk of self-diagnosis runs both ways — talking yourself into a label you don’t have, or, more dangerously, talking yourself out of help you genuinely need. A professional assessment is what gets you the right answer, and therefore the right support.
What to expect at an assessment
If the idea of being “assessed” feels daunting, here’s what it usually looks like. Tap each step. (This is what to expect — not a test to take yourself.)
Signs it’s worth getting assessed
This isn’t a checklist to diagnose yourself — it’s a prompt to reach out. If, for two weeks or more, you’ve noticed a persistent low or empty mood, a loss of interest in things you used to enjoy, ongoing changes in your sleep, appetite or energy, trouble concentrating, a heavy sense of worthlessness, or that you’re simply not functioning the way you usually do — those are good reasons to speak to a professional. You don’t need to be certain, and you don’t need to wait until things are unbearable. Seeking help early is wise, not premature.
If you’re having darker thoughts: If you’ve been having thoughts that life isn’t worth living, or of harming yourself, please reach out for support straight away — you don’t have to wait for a diagnosis. Talk to someone you trust, and you can find immediate help on our crisis support page.
The good news
It’s worth holding on to this: depression is one of the most treatable conditions in mental health, and a clear diagnosis is the beginning of feeling better, not a verdict to dread. Once you know what you’re dealing with, there are genuinely effective paths forward — see our guide to the treatments for depression. If you’d like to know what that first appointment actually feels like, our piece on your first therapy session may help too.
Key takeaways
- Depression is diagnosed by a trained professional — not by a quiz, a checklist, or yourself.
- Diagnosis centres on a clinical conversation, guided by established criteria (symptoms most days for 2+ weeks).
- Questionnaires like the PHQ-9 are screening aids, not a diagnosis on their own.
- A doctor may rule out physical causes, such as a thyroid problem, that can mimic depression.
- Persistent low mood or loss of interest for two weeks or more is a good reason to seek an assessment.
- Depression is highly treatable — a diagnosis is the first step toward feeling better.
Frequently asked questions
How is depression diagnosed?
Through a clinical assessment with a qualified mental health professional — a structured but warm conversation about your mood, thoughts, sleep, energy and how long things have been difficult, measured against recognised diagnostic criteria. A doctor may also run tests to rule out physical causes. There’s no single blood test or scan that detects depression on its own.
Can I diagnose my own depression with an online test?
No — online tests and questionnaires can raise awareness and suggest it’s worth getting help, but they can’t diagnose you. Depression’s symptoms overlap with several other conditions that need different treatment, so an accurate diagnosis requires a professional. Use an online result as a nudge to book an assessment, not as the answer itself.
What’s the difference between sadness and depression?
Sadness is a normal, usually passing response to life’s difficulties. Depression is more persistent and pervasive — a low or empty mood, or loss of interest, that lasts most of the day for at least two weeks and begins to interfere with everyday life, often alongside changes in sleep, appetite, energy and concentration. When low feelings settle in and stop lifting, it’s worth getting checked.
Who can diagnose depression?
A qualified mental health professional — such as a clinical psychologist or psychiatrist — diagnoses depression through clinical assessment. A GP can also assess and screen for it, and may order tests to rule out physical causes. The key point is that it’s a trained professional, not a self-test, who makes the diagnosis.
How long does it take to be diagnosed?
Often a single thorough assessment is enough to reach a working diagnosis, though sometimes a professional will want to see how things develop over a couple of appointments, or wait on medical tests that rule out other causes. Either way, you don’t have to have it all figured out before you go — that’s the professional’s job.
Wondering if it’s depression? You don’t have to guess
A proper assessment can replace months of uncertainty with clarity and a way forward. Dr. Prerna Kohli offers compassionate assessment and therapy for depression, in Gurgaon and online worldwide.
Book a Session WhatsApp → 98118 62338
About Dr. Prerna Kohli
Dr. Prerna Kohli is a clinical psychologist with over 30 years of practice, based in Gurugram. She holds a PhD from Aligarh Muslim University, where she was a four-time gold medallist, and received the ‘100 Women Achievers of India’ award from the President of India in 2016. A TEDx speaker and published author, she works with individuals, couples, and families through her private practice — in clinic in Gurugram and online worldwide — with a particular speciality in NRI mental health.