What to explain
Explain what changed and what you cannot manage.
My thinking changed around [date]. I can describe any changes in my mood and interest, including when they began. These are the tasks I now struggle with. Could we review depression, any past periods of unusually high energy, my PHQ-9 answers and safety? I also want to discuss sleeping problems, medicines, alcohol or other substances, and physical symptoms that may need assessment.
Questions to take in
Ask what needs assessment and what happens next.
- Do my symptoms and daily difficulties support depression, and what information is still needed before making a diagnosis?
- Does any past period of less need for sleep, high or irritable mood, fast thoughts, increased activity, risky behavior, or psychosis require a bipolar assessment?
- How will you assess suicide and self-harm risk beyond my PHQ-9 total and item 9 answer?
- Could any prescription, supplement, alcohol, cannabis, stimulant, sedative, steroid, missed dose, interaction, or withdrawal cause sleeping problems or worsen my mood or thinking?
- Which symptoms justify TSH, CBC, ferritin, B12, glucose, kidney, liver, pregnancy, infection, or sleep testing, and which tests are not needed?
- If my mood improves but I still struggle to remember, concentrate or think quickly, when should we check my medicines and sleeping problems or arrange a cognitive or neurological assessment?
- What treatment choices suit my symptoms, earlier treatment response, age, pregnancy or breastfeeding status, medical conditions, medicine interactions, cost, and preferences?
- When should follow-up occur, what change should we measure, and which symptoms mean I should seek urgent help before that visit?
Assessments that may help
What each check can tell you.
Choose tests according to symptoms, history, examination, medicines and earlier results. Age and pregnancy can also change which checks are useful. No blood test diagnoses depression.
PHQ-9 Depression Questionnaire
PHQ-9 records nine symptoms from the previous two weeks. Keep each answer, the 0 to 27 total, daily impact, and any answer to item 9.
Read the test guideMood Disorder Questionnaire (MDQ)
MDQ asks about past periods of unusually high or irritable mood, less need for sleep, increased activity, fast speech, racing thoughts, confidence, spending, or risky behavior.
Read the test guideMedication Review
A medication review checks whether a medicine, interaction, missed dose, withdrawal, alcohol, cannabis, stimulant, or supplement could cause sleeping problems or affect mood, energy, memory, or concentration.
Read the test guideTSH Blood Test
TSH helps check thyroid function when symptoms or history justify it. A normal or abnormal thyroid result still needs interpretation with symptoms and any follow-up thyroid tests.
Ask your doctorCBC with Differential
A CBC can identify anemia and some blood-cell changes. It does not diagnose depression or show why the anemia occurred.
Read the test guideFerritin Blood Test
Ferritin measures stored iron. It may help when there is heavy bleeding, pregnancy, a limited diet, blood donation, surgery, gut disease, or anemia.
Read the test guideVitamin B12 Blood Test
Vitamin B12 testing may help when there's a limited diet, gut or weight-loss surgery, poor absorption, metformin or acid-reducing medicine use, anemia, numbness, balance trouble, or memory change.
Read the test guideSleep Study (PSG)
A sleep study can assess sleep apnea when loud snoring, gasping, breathing pauses, morning headaches, dry mouth, or marked daytime sleepiness occurs.
Read the test guideBaseline Cognitive Assessment
A baseline cognitive assessment may help when memory or thinking problems persist, progress, seem greater than the mood symptoms, or interfere with safety and independent daily tasks.
Read the test guideBefore the appointment
Bring a short account and useful records.
When low mood, loss of interest, brain fog, sleeping problems, low energy, appetite change or hopelessness began. Note whether symptoms are constant or occur in episodes.
Your PHQ-9 form with all nine answers, total, date and language. Include the separate daily-difficulty answer if the form has one.
Two examples of tasks becoming slower, inaccurate, unfinished or unsafe. Choose from reading, work, school, cooking, driving, childcare, medicines, money or conversation.
Prescriptions, over-the-counter products, supplements, alcohol and other substances. Include dose, timing, missed doses, changes and withdrawal symptoms.
Sleep and wake times and relevant symptoms: snoring, gasping, breathing pauses, nightmares, restless legs, night work or daytime sleepiness. Mention falling asleep while driving directly.
Any past episode of less need for sleep with high or irritable mood, fast speech or thoughts, increased activity, spending, sexual risk, aggression, grand beliefs or psychosis.
Earlier records about mental health, sleeping problems, physical health and thinking difficulties. Include previous thyroid, blood-count, iron, B12 or other tests, along with pregnancy or menopause history when relevant.
If you want a trusted person involved, bring their observations about how you sleep, behave, remember things and care for yourself. Include safety concerns and times you seemed unlike yourself.
For example: During the last week, I reread the same email four times, missed two bill dates, and stopped cooking because I could not follow the steps.
How the doctor assesses this
What supports a depression assessment
- You have felt low or lost interest in things most days for at least two weeks. This affects work, school, relationships, self-care, how you sleep or eat, or your safety.
- Describe whether thinking problems began before, during or after the change in mood. The dates help the doctor assess what may be contributing. Mood and thinking may improve at different speeds.
- Talk directly about a PHQ-9 answer, suicidal thought, self-harm history, manic or psychotic symptom, or being unable to care for yourself. The total score alone isn't enough.
What else may need checking
- Depression needs direct assessment when low mood or loss of interest lasts most days for at least two weeks and interferes with daily life.
- Bipolar disorder needs separate assessment after any distinct period of unusually high or irritable mood, much less need for sleep, increased activity, fast speech, risky behavior, or psychosis.
- Sleep apnea needs checking when brain fog happens with loud snoring, gasping, witnessed breathing pauses, morning headache, dry mouth, or severe daytime sleepiness.
- Suspect a medicine or substance when symptoms began after a new product, dose change, missed doses, withdrawal, more alcohol, cannabis, stimulants, sedatives, or steroid use.
- A physical or neurological cause needs more attention when other symptoms are present. These include fever, weight change, bleeding, weakness, numbness, speech change, fainting, seizure, severe headache, or a steady loss of daily skills.
What to understand before choosing care
Agree the treatment and follow-up plan.
- Keep every PHQ-9 answer. Two people with the same total may need different safety questions and treatment discussions.
- Describe any period of unusually high energy, little need for sleep, fast thoughts, risky behavior or psychosis before starting or changing an antidepressant.
- Agree a safe plan before changing an antidepressant, mood stabilizer, sedative, stimulant or steroid. Alcohol or other drug dependence may also need a supervised withdrawal plan.
- Use physical symptoms, examination findings, medicines and history to guide tests. Diet, bleeding, pregnancy, surgery, infection and family history can make a particular check useful.
- Regular sleep and meals, enough fluid, suitable activity and contact with a trusted person can support health while assessment and treatment continue.
What the research found
What research says about thinking and recovery.
A review published in 2025 found 99 eligible studies and pooled results from 69 studies involving 4,639 people. More than 95% of the measured cognitive changes were small, negligible or not statistically significant.
The 2025 review could not exclude practice effects from repeating thinking tests. Its average results cannot predict whether one person's concentration or memory will improve.
A 2026 review included 49 studies, with 37 in the meta-analysis, involving 6,991 participants. Links between thinking skills and daily function were generally weak or moderate; more than half were not statistically significant.
The 2026 review found limited evidence about whether early cognitive results predict later daily function. Assessment should include the person's difficulties at work, home or school and any safety concerns, even when a test score suggests little difficulty.
A 2025 review of treatment in older adults found different cognitive results across medicines and studies. Some thinking skills improved, but the differences between trials prevent a simple prediction of recovery.
How age and life stage affect the assessment.
Children and teenagers may become irritable, fall behind at school, withdraw, have sleeping problems, eat differently, report physical complaints or take risks before saying they feel sad.
Adolescents need age-appropriate depression and suicide-risk assessment. The adult PHQ-9 and its item 9 should not be used as the only suicide screen.
NICE reports that women are diagnosed with depression 1.5 to 2.5 times as often as men. Men may show irritability, substance use, risk-taking, or physical complaints and may seek help later.
For people aged 18 to 25 or at increased risk of suicide, NICE advises a review for suicidal thoughts one week after starting an antidepressant or increasing its dose.
During pregnancy and the first year after birth, an assessment should check for depression, anxiety, bipolar disorder and suicide risk. It should also cover medicines, sleeping problems, available support and signs of postpartum psychosis. ACOG advises bipolar screening before depression medicine starts.
During perimenopause or menopause, describe any sleeping problems, changes in mood or concentration, migraines or changes in bleeding. Ask whether iron or thyroid problems also need checking. Do not assume hormones explain everything.
In older adults, depression may appear as low motivation, physical complaints, or thinking problems. The doctor may also need to check medicines, pain, sleeping problems, hearing and vision, and assess for delirium, stroke or dementia.
If the answer is no
If a broad blood panel is not needed
Depression is assessed through symptoms, their duration and their effect on daily life. An interview, examination and selected tests can identify medicines or illnesses causing similar problems. Ask what each proposed test would change.
What changes the answer
- Describe the whole change. Include sleeping problems and changes in appetite, energy, movement, concentration, interest and daily life, with the date symptoms began.
- Ask what a test would check. A medicine change, infection, thyroid symptom, bleeding or weight change may justify a targeted check.
- Ask what has been considered. Find out which medicine effects and health conditions fit your history and which tests could change care.
- Agree when you'll come back. Ask which new symptoms or lack of treatment response should prompt another assessment.
United States, United Kingdom, and Australia
Who to contact about depression and brain fog.
US United States
Book a depression and medical assessment. Ask the clinician to assess your safety and discuss any past symptoms of bipolar disorder. Review your medicines, alcohol and other substances, and have a physical examination....
- Start with primary care, a psychologist, a psychiatrist, or another licensed mental health clinician. A positive depression screen needs further assessment before diagnosis or treatment.
- USPSTF recommends depression screening for adults, including pregnant, postpartum, and older adults, when systems can provide assessment, treatment, and follow-up.
- A routine clinician visit is not enough when someone may harm themselves, cannot stay safe, has mania or psychosis, or develops postpartum psychosis. Use urgent or emergency mental health care.
UK United Kingdom
See a GP or mental health service. Take the PHQ-9 answers, symptom dates, a medicine list, notes about sleeping problems, bipolar history, physical symptoms and examples of lost daily function.
- A GP or mental health professional should assess symptoms, duration, daily impact, earlier episodes, physical health, medicines, alcohol or drugs, social conditions, bipolar history, and suicide risk.
- NICE says assessment should not rely only on a symptom count. Treatment choice should reflect severity, needs, preferences, earlier response, risks, and access.
- NHS Talking Therapies may accept self-referral in England, but urgent safety, mania, psychosis, or serious physical symptoms need faster clinical care.
AU Australia
Book a GP or mental health appointment. Ask the doctor to assess your safety and check for bipolar disorder. Review your medicines, alcohol or drug use, sleeping problems,...
- Start with a GP, psychologist, psychiatrist, or community mental health service. Assessment usually includes discussion, a questionnaire, physical health, medicines, family history, and any past mania.
- Healthdirect says to talk to a health professional if low mood lasts at least two weeks and affects home, work, or school.
- Immediate danger, suicidal intent, inability to stay safe, mania, psychosis, or postpartum psychosis needs emergency assessment rather than a routine appointment.
Safety
What to note while you wait.
- Write down when symptoms began. Include sleeping problems and changes in mood, interest, energy, concentration or appetite. Note relevant medicines, alcohol or other substances, pain, illness and menstrual or menopause changes. You do not need to monitor every symptom every day.
- Choose one or two concrete examples: a missed medicine dose, a forgotten bill, losing track of a conversation, much slower reading or food left cooking. Include the consequence, especially any safety concern.
- Keep sleep and wake times regular when possible. Note snoring, gasping, morning headaches, dry mouth, nightmares, restless legs and daytime sleepiness if they occur.
- Eat and drink regularly unless you have different medical instructions. Mention a repeated link between worse symptoms and missed meals, dehydration, alcohol or medicine timing.
- Choose activity you can safely manage. Stop the activity and seek prompt help if it causes chest pain, fainting or severe breathlessness. Describe delayed or prolonged worsening after activity before increasing it.
- Do not test a theory by stopping or adding medicine, taking extra supplements, staying awake, fasting or drinking alcohol. Repeatedly taking the PHQ-9 to obtain a different score will not clarify the cause.
Source checked
Sources behind this handout.
- 01
Kroenke K et al. PHQ-9 validity study. Journal of General Internal Medicine. 2001. PMID: 11556941.
Source - 02
Ahern E et al. Change in cognitive function during major depressive disorder. Neuropsychology Review. 2025. PMID: 38315296.
Source - 03
Semkovska M et al. Executive function after remission from major depression. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. 2026. PMID: 40967524.
Source - 04
Nelson JC et al. Depression treatments and cognition in older adults. American Journal of Geriatric Psychiatry. 2025. PMID: 39366871.
Source - 05
Ahern E et al. Thinking skills and daily function in major depressive disorder. Clinical Psychology Review. 2026. PMID: 42119551.
Source - 06
National Institute of Mental Health. Depression symptoms, diagnosis, age differences, medical causes, and treatment. Revised 2024.
Source - 07
MedlinePlus: depression screening and follow-up.
Source - 08
US Preventive Services Task Force. Depression and suicide-risk screening in adults. 2023.
Source - 09
NICE NG222: Depression in adults, treatment and management.
Source - 10
American College of Obstetricians and Gynecologists. Mental health screening during pregnancy and postpartum. Current patient-screening guidance.
Source - 11
Healthdirect Australia: depression.
Source