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How to Diagnose Mental Health Issues: A Guide for Adults and Older Adults

South Asian participant in his late 30s reviewing diagnostic assessment paperwork with the psychologist in a health clinic.

Last Updated on 07/10/2026 by Daniel G. Taylor

Estimated reading time: 14 minutes

Professionals diagnose mental health issues through conversation and observation. No scan does the work for them. Instead, careful elimination narrows the field.

I know the process from the inside. Bipolar I disorder entered my life in 1996, and the diagnosis rearranged everything I thought I knew about my own mind.

Eventually, stability came in 2001. Since 2003, Interpersonal and Social Rhythm Therapy has protected it, one anchored routine at a time.

I still carry the diagnosis. I do not carry a psychosocial disability, and I am not an NDIS participant. That distinction, in fact, sits at the heart of this guide.

Many readers, however, arrive here with a diagnosis already in hand. Some received it decades ago, in a hospital ward or a GP clinic long since closed.

This guide covers who can diagnose, how assessment works, why an old diagnosis may need fresh eyes, and what the NDIS asks for when diagnosis meets daily life.

October is Mental Health Month, with World Mental Health Day on 10 October. This year, Mental Health Australia chose the theme Together We Thrive, which places connection at the centre of wellbeing.

In that spirit, this guide forms part of The SALT Foundation’s Mental Health Month series. The series also updates two other posts, one that explains what the NDIS covers for mental health and what psychosocial disability looks like in everyday life. Next week a new post, a guide for families and carers supporting someone living with schizophrenia completes the set.

Key Takeaways

  • Professionals diagnose mental health issues through conversation and careful assessment, as no scan can replace their insight.
  • Many Australians live with undiagnosed mental conditions, making accurate diagnosis essential for effective treatment.
  • A current diagnosis can guide treatment, separate mental and physical symptoms, and support NDIS applications.
  • Telehealth assessments by qualified psychiatrists and psychologists provide valid diagnoses, enhancing access to care.
  • An updated report is critical for NDIS applications, as it shows how a condition currently affects daily life.

Table of Contents

What Does It Mean to Diagnose Mental Health Issues?

To diagnose mental health issues, a professional identifies a specific condition from your symptoms, history and circumstances.

A diagnosis is not a verdict. Instead, it is a working explanation, tested over time against how you respond to treatment.

Mental health conditions touch most families. More than two in five Australians aged 16 to 85 have experienced a mental disorder in their lifetime, according to the Australian Bureau of Statistics.

The same ABS study found fewer than half of people with a recent mental disorder saw a health professional about it. As a result, many people live for years without a name for what they carry.

Why a Diagnosis Still Matters in Midlife and Beyond

A diagnosis works like a map. Without one, you guess at what might help.

I guessed for years. Before my diagnosis, people read me as arrogant. In fact, my self-assurance came from the grandiosity of the disorder, not from my character.

For adults in their 40s, 50s and 60s, a current diagnosis does three jobs:

  • It points treatment in the right direction, including medication reviews as your body ages.
  • Equally, it separates mental health symptoms from physical conditions that can imitate them.
  • Finally, it anchors the evidence the NDIS needs, and the NDIS must receive your application before you turn 65.

Who Can Diagnose Mental Health Issues in Australia?

Three professionals hold the training to diagnose mental health conditions in Australia. Each plays a different part.

Your GP

Your GP usually opens the first door. A GP can assess you, rule out physical causes, start some medications and refer you to a specialist.

For complex or long-standing conditions, however, expect a referral to a psychiatrist or psychologist.

Psychiatrists

Psychiatrists are medical doctors who specialise in mental health. They diagnose the full range of conditions, prescribe medication and lead care for severe and enduring illness such as schizophrenia.

Clinical psychologists

Clinical psychologists specialise in psychological assessment and therapy. They diagnose most conditions and often work beside a psychiatrist on complex cases.

Free support in Victoria

Victorians aged 26 and over can also contact a Mental Health and Wellbeing Local. Support costs nothing, and you need no referral from a doctor.

However, Locals are not crisis services. If you or someone near you is in danger, call 000. For crisis support at any hour, call Lifeline on 13 11 14.

Can Online Tools or Telehealth Diagnose Mental Health Issues?

Search engines and AI chatbots field this question every day. The short answer: online tools screen, and professionals diagnose.

Free screeners help you put words to how you feel. Beyond Blue’s anxiety and depression test uses the K10, a 10-question measure of distress.

Beyond Blue states plainly that only a mental health professional can give you a diagnosis. Take your result to your GP and let it open the conversation.

Similarly, apps and AI chatbots sit in the same category. They can prompt reflection, but none can weigh your history, physical health and circumstances.

Telehealth, by contrast, works differently. A psychiatrist or psychologist can assess you by video, and that diagnosis carries the same weight as one made in a clinic.

Telehealth also suits people who find leaving home hard, or who rely on public transport to reach appointments. Ask your GP whether a video consult fits your situation.

Not sure where to start? Medicare Mental Health offers free advice on 1800 595 212 on weekdays and connects callers with local services. Like the Locals, it is not a crisis service.

How to check a practitioner’s registration

Before you book any clinician, in person or online, check their registration. Ahpra’s online register of practitioners is free, updated continuously and lists every registered health practitioner in Australia.

Checking takes a few minutes:

  • Go to ahpra.gov.au and choose the option to look up a health practitioner.
  • Type the practitioner’s name exactly as they registered it, and select their profession, such as psychology or medical.
  • Open their entry. Confirm the status shows as registered, then check the registration type and any conditions listed.
  • For a psychiatrist, look for psychiatry listed as their specialty.
  • If the name does not appear, or the details look wrong, call Ahpra on 1300 419 495.

Conditions do not always mean danger, though. A practitioner with conditions can still practise, but the conditions may limit what they can do.

How Do Professionals Diagnose Mental Health Issues?

Mental illness does not show up on an X-ray. Researchers have trialled a blood test to support bipolar diagnosis, but no test yet replaces a skilled clinician.

Instead, professionals combine five methods.

1. Clinical interviews

The interview sits at the heart of diagnosis. Expect questions about your symptoms, when they began, how they shape your days, and your personal and family history.

2. Physical exams and tests

Physical illness can wear the mask of mental illness. For example, thyroid problems, infections and medication side effects can all change mood or thinking.

The older you are, the more this step matters. Ask for it if nobody offers.

3. Psychological assessments

Questionnaires and structured interviews measure specific symptoms and track them over time.

4. Observation

Meanwhile, the professional notices how you speak, move and respond. Family members or support workers can also add what they see across a whole week.

5. Diagnostic criteria

Clinicians match what they find against standard criteria, mainly the DSM-5-TR, the current edition of the Diagnostic and Statistical Manual of Mental Disorders.

What to Expect During a Diagnostic Assessment

My first assessment took place during my first manic episode. At first, I believed nothing was wrong with me.

If I could convince the doctors of that, I reasoned, they would let me leave the psychiatric hospital.

Most assessments run calmer than mine. A typical one looks like this:

  • You answer questions about your symptoms, history, relationships and work.
  • The professional may arrange a physical exam or blood tests.
  • You may complete one or more questionnaires.
  • Diagnosis may take several sessions, particularly for complex conditions.

Be honest, even when honesty feels risky. The professional is there to help, not judge. To support, not challenge. To care, not neglect.

Preparation helps more than most people expect. Harriet Dixon, a Psychosocial Recovery Coach at The SALT Foundation, hears one regret above all others.

“The thing people most often tell me is that they wish they had written things down first,” she says.

After years of appointments, Dixon explains, anyone can go blank when a new clinician asks what brings them in. Her solution fits on a single sheet.

“Take one page with three things on it: what has changed, what has helped, and what a hard day looks like for you,” Dixon says.

She also suggests bringing a support person along. “They often remember what you forget,” she said.

When Your Diagnosis Is Decades Old

Many adults living with severe and enduring mental illness received their diagnosis 20 or 30 years ago. The language has moved since then.

In 2013, the DSM-5 retired the subtypes of schizophrenia, including paranoid schizophrenia, as Psych Central explains. As a result, the diagnosis today reads simply as schizophrenia.

Diagnoses also shift as a condition reveals itself over time. Depression can be reviewed as bipolar disorder. Similarly, schizophrenia can be reviewed as schizoaffective disorder.

None of this means your old diagnosis was wrong. Rather, it means the paperwork may describe the person you were, not the person you are.

A review with your current psychiatrist or GP brings the record up to date. It also gives the NDIS evidence from someone who knows you now.

My own experience, however, runs the other way. The wording of my diagnosis has never changed.

I don’t read early reports or have access to them. My GP keeps my records and refers me to a psychiatrist as needed, which has happened once in 25 years.

For anyone whose condition has shifted, or whose records sit scattered across services, a review earns its time.

What an old letter cannot tell the NDIS

Greg Smith, Chief Operating Officer at The SALT Foundation, sees the gap often. “A diagnosis letter from 20 years ago tells the NDIS you had a condition then,” he says.

“It says very little about how that condition affects your life today, and that is what the NDIS needs to understand.”

So when someone arrives with only an old letter, SALT encourages them to see their current GP or psychiatrist first. A fresh report describes the person as they are now, written by someone who knows them.

“That gives the application a much stronger footing,” Smith said.

From Diagnosis to NDIS Evidence

A diagnosis opens the conversation with the NDIS. However, it does not finish it.

The NDIS funds support for the daily impact of a condition, not the clinical treatment of the condition itself. Function, not label, decides eligibility.

For psychosocial disability, the NDIS asks for a statement from a treating health professional covering:

  • how long they have worked with you
  • evidence of your mental health condition, with a diagnosis if one is available
  • treatments you have tried, and any you have not, with reasons
  • how your condition affects your everyday life.

The Evidence of Psychosocial Disability form gives your professional a structure for that statement. The NDIS also asks for a functional capacity assessment, such as the LSP-16, HoNOS or WHODAS.

Your GP and psychiatrist are not the only people who can help. Psychiatric nurses, mental health occupational therapists, social workers and trained peer workers can also provide evidence.

If the forms feel like a wall, you need not climb it alone. Help with your NDIS application sits closer than you might think.

After the Diagnosis: Treatment, Recovery and Daily Life

A First Nations female SALT Psychosocial Recovery Coach in her early 30s sitting at an outdoor wooden table in a leafy Melbourne park with a white Australian male NDIS participant in his early 40s, collaboratively reviewing a goal-setting notebook during a planning session in soft morning sunlight.

A diagnosis can bring relief. At last, the experience has a name. But a name is only a beginning.

Stigma arrived almost as soon as people found out about my mental health condition. Yet nothing I did could make them take back unkind words.

So I changed tactics. I led with my condition and what I needed, which forced people to confront the issue head on, in advance.

After diagnosis, most people move through some version of these steps:

  • Discuss treatment options with your doctor.
  • Begin a treatment plan, which may combine medication and therapy.
  • Learn about your condition from reliable sources.
  • Build routines around sleep, meals and activity.
  • Connect with peer support, community groups or services.

Where daily support fits

Clinical care from your GP, psychologist or psychiatrist runs through Medicare and the public health system. Meanwhile, the NDIS sits alongside it for people whose condition creates lasting barriers in daily life.

For many people, that support arrives at the front door. Support workers help with shopping, appointments, transport and the household tasks an illness can push out of reach.

Psychosocial recovery coaching works on the bigger picture: routines, self-advocacy and goals that belong to you.

Catherine, a Support Worker with The SALT Foundation, measures progress in small, steady steps. “A good week is not about big moments,” she says.

“It is the same familiar face turning up at the same time, so there are no surprises.”

Together, they shop, get to appointments and share a coffee and a chat along the way. Then the small wins arrive: someone ready at the door, a long-avoided phone call finally made, a story about the week offered before she asks.

“Those things build slowly,” Catherine said, “and they matter.”

Seeing the person first

A diagnosis describes a condition. It does not define you, and recovery remains possible at any age.

Roger Donnelley, Chief Executive Officer of The SALT Foundation, knows many people SALT supports have carried a serious mental illness label for most of their adult lives. Some, he notes, have been treated as that label by almost every service they have walked into.

For that reason, SALT starts by listening. Staff ask about each person’s interests, history and hopes for life.

“A diagnosis is part of someone’s story,” Donnelley says. “It is never the whole story.”

Action Steps

  1. Book a long appointment with your GP and say you want to talk about your mental health.
  2. Write down your symptoms, when they started, and how they affect sleep, self-care, money and relationships.
  3. Gather old reports and diagnosis letters, then ask your treating professional whether they need a review.
  4. Ask for a physical health check to rule out medical causes, particularly if you are over 45.
  5. If you are under 65 and your condition limits daily life, ask your treating professional about the Evidence of Psychosocial Disability form.
  6. If you live in Victoria and are 26 or over, contact a Mental Health and Wellbeing Local for free support without a referral.

Frequently Asked Questions

How do I know if I have a mental health issue?

Watch for changes in mood, thinking, sleep or behaviour that last for weeks and get in the way of daily life. Only a professional can confirm a diagnosis, so raise what you notice with your GP.

What are the steps to get a mental health diagnosis in Australia?

Book a GP appointment, describe your symptoms honestly, and complete any tests or questionnaires. Your GP may diagnose you or refer you to a psychiatrist or psychologist. Victorian adults aged 26 and over can also contact a Mental Health and Wellbeing Local without a referral.

Can a psychologist diagnose mental health issues?

Yes. Clinical psychologists diagnose most mental health conditions. Psychiatrists diagnose the full range and can prescribe medication, while GPs diagnose and treat many common conditions such as depression and anxiety.

How much does a private psychiatric evaluation cost?

Fees vary from one psychiatrist to the next. Even so, a GP referral lets you claim a Medicare rebate, so ask the clinic about the gap before you book. By contrast, public mental health services and Mental Health and Wellbeing Locals cost nothing.

Are online mental health assessments reliable?

Reputable screeners such as the K10 reliably measure distress, but they cannot diagnose. Instead, use your result as a starting point for a conversation with your GP, not as an answer.

My diagnosis is very old. Do I need a new one?

Not necessarily a new diagnosis, but an updated report helps. The NDIS asks how long your treating professional has worked with you, so current evidence carries more weight.

Do I need a diagnosis to apply for the NDIS?

In fact, the NDIS describes a diagnosis as helpful if available. Your evidence must still show your condition and how it affects everyday life, and the NDIS must receive your application before you turn 65.

Conclusion: Your Diagnosis Is a Beginning, Not a Verdict

Professionals diagnose mental health issues with time, questions and care. Your part, meanwhile, is honesty, preparation and persistence.

If your diagnosis is old, refresh it. If it is new, learn it. And when it blocks the ordinary business of living, the NDIS may help close the gap.

Mental Health Month reminds us of something simple: together, we thrive. Nobody has to walk from diagnosis to support alone.

The SALT Foundation supports adults across Melbourne, Frankston and the Mornington Peninsula with daily living support and recovery coaching. Talk to our team about what support could look like for you.

Family member, carer or clinician? Make a referral, and our team will be in touch.