Relevant Psychiatric and Psychosocial Investigations: A Complete Clinical Guide

Relevant psychiatric and psychosocial investigations are the targeted bedside assessments, laboratory tests, imaging studies, screening instruments and social enquiries used to clarify a mental-health presentation, identify a reversible medical or substance-related cause, establish treatment safety, assess risk and plan recovery. A good investigation plan is not a request for every available test. It is a reasoned response to the patient’s history, mental state examination, physical findings, age, medication exposure, risk and local epidemiology.

Learning objectives

By the end of this guide, the learner should be able to:

• Explain why most primary psychiatric disorders are clinical diagnoses rather than diagnoses made by a single laboratory test.
• Choose immediate bedside observations, physical examinations and focused investigations according to the presentation.
• Recognise red flags for delirium, first-episode psychosis, new-onset mania, cognitive decline, catatonia, seizures and substance-related emergencies.
• Use screening and symptom-rating instruments without confusing a score with a diagnosis or risk decision.
• Complete a culturally sensitive psychosocial assessment, including collateral history, functioning, safeguarding, capacity and social determinants of health.
• Document the clinical question, result, interpretation, action and follow-up for every investigation.

1. The central principle: investigate the patient, not the label

Psychiatric assessment starts with the patient’s story, collateral information, risk assessment, physical examination and mental state examination. Investigations answer specific questions:

2. A practical investigation sequence

1. Stabilise and triage. Assess airway, breathing, circulation, disability, exposure, consciousness, agitation, violence risk, self-harm risk and immediate access to dangerous means.
2. Repeat vital signs and bedside measures. Record temperature, pulse, blood pressure, respiratory rate, oxygen saturation, capillary glucose, level of consciousness, pain and hydration status. Repeat abnormal observations.
3. Take a complete history and collateral history. Establish onset, time course, baseline function, medications, substances, medical and neurological illness, pregnancy possibility, trauma, psychosocial stressors and previous episodes.
4. Perform a focused physical and neurological examination. Look for infection, endocrine disease, intoxication or withdrawal, focal neurological signs, head trauma, malnutrition, movement disorder and medication toxicity.
5. Define the clinical question. Do not order a test merely because it is customary. State what you are looking for and what action will follow a positive or negative result.
6. Order targeted investigations. Select bedside tests, blood tests, toxicology, ECG, imaging or specialist investigations according to risk and findings.
7. Interpret, act and communicate. Document the result, significance, action, responsible clinician and time for review. A test that is ordered but not acted upon is an unsafe investigation.

3. Immediate bedside assessment and physical examination

3.1 Observations that should not be missed

• Temperature: fever suggests infection, inflammatory disease, serotonin toxicity, neuroleptic malignant syndrome or severe withdrawal; hypothermia may occur in exposure, endocrine failure, intoxication or sepsis.
• Pulse and blood pressure: tachycardia, hypertension, hypotension or postural change may indicate intoxication, withdrawal, dehydration, sepsis, pain, mania, medication effects or autonomic instability.
• Respiratory rate and oxygen saturation: detect opioid or sedative respiratory depression, pneumonia, asthma, pulmonary disease and metabolic decompensation.
• Capillary blood glucose: perform early in altered behaviour, confusion, collapse, seizure, reduced consciousness, diabetes, suspected overdose or poor oral intake.
• Level of consciousness and attention: reduced arousal or impaired attention strongly raises concern for delirium, intoxication, withdrawal, seizure or an encephalopathy.
• Weight, BMI and waist circumference: provide a baseline before and during antipsychotic treatment and identify malnutrition or metabolic risk.
• Pregnancy status: ask privately and respectfully where pregnancy is possible before radiation, valproate, lithium or other potentially teratogenic treatment.

3.2 Focused physical examination

• General appearance: hydration, pallor, jaundice, cyanosis, odour of alcohol or chemicals, nutritional state, self-care and evidence of neglect.
• Neurological examination: pupils, speech, cranial nerves, power, tone, reflexes, sensation, coordination, gait, tremor, rigidity, clonus and involuntary movements.
• Signs of head injury: scalp injury, periorbital bruising, vomiting, amnesia, seizure or focal deficit.
• Endocrine clues: thyroid enlargement, tremor, heat or cold intolerance, weight change, hyperpigmentation, proximal weakness or Cushingoid features.
• Infection and inflammation: fever, meningism, rash, focal infection, lymphadenopathy, HIV-related illness or tuberculosis symptoms.
• Medication effects: akathisia, parkinsonism, dystonia, tardive movements, sedation, orthostatic hypotension, anticholinergic signs, bruising, jaundice and lithium tremor.
• Trauma and safeguarding: bruises, burns, genital injury, fractures or injuries inconsistent with the history require a safe, non-accusatory safeguarding response.

4. Core laboratory investigations

There is no universal psychiatric panel. A reasonable baseline set depends on the presentation, age, comorbidity, medication plan and available resources. In a new or medically unexplained presentation, consider the following groups and document why each is being requested.

4.1 Blood count and basic chemistry

4.2 Endocrine, nutritional and infectious investigations

• Thyroid-stimulating hormone with free T4 when indicated: thyroid excess can resemble anxiety, agitation or mania; thyroid failure can resemble depression, slowed thinking or cognitive impairment.
• Vitamin B12 and folate: consider in cognitive change, neuropathy, macrocytosis, malnutrition, restrictive diet, malabsorption or unexplained neuropsychiatric symptoms. Treat the cause, not only the number.
• HIV testing: offer with informed consent according to local policy when there is cognitive decline, psychosis, neurological disease, opportunistic infection risk or relevant exposure. Provide counselling and linkage to care.
• Syphilis testing: consider in new cognitive change, psychosis, neurological signs, ocular disease or risk exposure. A reactive screening result needs confirmatory interpretation and clinical correlation.
• Malaria and other infection tests: in Uganda and other malaria-endemic settings, fever, confusion or seizures require an appropriate malaria assessment. Consider tuberculosis, meningitis and other infections according to symptoms and immune status.
• Inflammatory markers: ESR or CRP may support evaluation of infection, inflammation or autoimmune disease but are non-specific and do not diagnose a psychiatric condition.
• Autoimmune or metabolic tests: reserve ANA, anti-neuronal antibodies, copper/ceruloplasmin, porphyrins, cortisol or other specialised tests for suggestive presentations or specialist advice.

4.3 Urinalysis and other specimens

• Urinalysis may identify infection, ketones, dehydration, renal disease or pregnancy-related clues. Do not diagnose a urinary infection from a positive dipstick alone in a patient without compatible symptoms.
• Urine or blood toxicology can support detection of substances but has limitations: false positives, false negatives, delayed detection, cross-reactivity, variable detection windows and inability to prove current impairment.
• Blood alcohol concentration can support an emergency decision, but clinical state, tolerance, time since use and co-ingestants matter more than a number alone.
• Obtain cultures, blood gases, ketones, lactate or other specimens when sepsis, respiratory failure, diabetic ketoacidosis, toxic ingestion or metabolic encephalopathy is possible.

5. ECG, metabolic baseline and medicine-safety investigations

5.1 When to obtain an ECG

• Before or soon after a QT-prolonging medicine when risk factors exist: cardiac disease, syncope, electrolyte abnormality, family history of sudden death, multiple interacting medicines, overdose, bradycardia or high doses.
• Before antipsychotic treatment when clinically indicated and during follow-up if symptoms, medicines or risk factors change.
• In suspected stimulant or tricyclic overdose, severe agitation with autonomic instability, chest pain, palpitations or unexplained collapse.

Record rhythm, rate, PR interval, QRS width and corrected QT. Correct hypokalaemia, hypomagnesaemia and other reversible causes of QT prolongation. Do not interpret a machine-generated QT value without considering heart rate, rhythm, technical quality and the whole clinical picture.

5.2 Antipsychotic baseline and follow-up

Before starting an antipsychotic, record personal and family cardiac history, weight, waist circumference, pulse, blood pressure, smoking status, alcohol and substance use, fasting glucose or HbA1c, lipids and relevant movement symptoms. Consider ECG and prolactin when indicated. Continue monitoring weight, metabolic measures, movement symptoms, sexual or menstrual effects and adherence. A baseline makes a later adverse effect recognisable and supports shared decisions.

5.3 Lithium and mood stabiliser safety

• Lithium: baseline weight/BMI, renal function, electrolytes including calcium, thyroid function, pregnancy status where relevant and ECG when cardiac risk exists. Recheck levels after initiation or dose change and whenever toxicity, dehydration, interacting medicine or a major change in sodium/fluid intake is suspected. Document the exact time of the last dose and blood sample because timing determines interpretation.
• Valproate: baseline weight, full blood count, liver function and pregnancy potential. Discuss reproductive risks and use local specialist guidance. Investigate abdominal pain, vomiting, jaundice, unusual bruising, severe lethargy or encephalopathy urgently.
• Carbamazepine: consider full blood count, liver function, renal function, sodium and relevant genetic or infection-risk guidance. Review enzyme-inducing interactions and symptoms of severe skin reaction or marrow suppression.
• Lamotrigine: no routine serum level is usually useful; titrate carefully and treat a new widespread rash, mucosal lesion, fever or systemic illness as a potential serious reaction.

6. Presentation-specific investigations

6.1 First-episode psychosis

First-episode psychosis deserves a broad but targeted assessment because the probability of a medical, neurological or substance-related cause is higher than in a well-established, stable disorder. Investigate:

• Onset and progression: abrupt or gradual, fluctuating or continuous, relation to sleep loss, substances, medicines, infection or trauma.
• Full physical and neurological examination, including cognition, attention, focal deficits, movement disorder and signs of intoxication or withdrawal.
• Bedside glucose, full blood count, electrolytes/renal function, liver function, calcium, thyroid tests, pregnancy testing where relevant and HIV/syphilis or other infection testing when indicated by risk and local policy.
• Urine toxicology when it will alter management, while recognising detection-window limitations.
• ECG and metabolic baseline before antipsychotic treatment; consider neuroimaging or EEG for atypical features.
• Further specialist investigations for seizures, autoimmune encephalitis, Wilson disease, neurodegeneration, endocrine disease or other rare causes only when the history or examination supports them.

6.2 Delirium and acute confusion

Delirium is a medical emergency until proven otherwise. Confirm acute or fluctuating change from baseline, test attention and level of arousal, seek collateral history and search for a precipitant.

1. Check airway, breathing, circulation, oxygen saturation, temperature and capillary glucose.
2. Use a structured tool such as the 4AT or CAM where trained, but do not allow a negative screen to overrule clear clinical concern.
3. Perform medication reconciliation, including over-the-counter, herbal, anticholinergic, sedative and recently stopped medicines.
4. Investigate infection, hypoxia, dehydration, electrolyte disturbance, renal or hepatic failure, pain, urinary retention, constipation, withdrawal, intoxication, seizure and head injury according to findings.
5. Escalate for CT, lumbar puncture, EEG or specialist review when focal deficit, meningism, seizure, severe headache, immunosuppression, unexplained reduced consciousness or persistent unexplained delirium is present.

6.3 New-onset mania or severe agitation

Assess sleep, prescribed medicines, steroids, stimulants, antidepressants, thyroid symptoms, substance use, infection, neurological symptoms and risk to self or others. Obtain glucose, electrolytes, renal/liver function, thyroid tests, pregnancy status and toxicology when relevant. ECG is important before medicines that affect conduction or QT, and before treating a possible overdose. Look for delirium, catatonia, neuroleptic malignant syndrome, serotonin toxicity and severe dehydration.

6.4 Cognitive impairment or dementia

• Establish baseline cognition and function from a reliable informant: onset, progression, instrumental activities, personality change, sleep, hallucinations, falls, driving and medication management.
• Check reversible contributors: medication burden, depression, delirium, hearing/vision impairment, thyroid disease, B12/folate deficiency, infection, metabolic disease, alcohol and sleep disorders.
• Use a cognitive instrument such as MoCA or MMSE as a baseline, not as a stand-alone diagnosis. Document language, education, sensory impairment and cultural context.
• Assess gait, parkinsonism, focal deficits, seizures, falls and head injury. Consider CT or MRI when onset is rapid, focal signs exist, there is gait disturbance, young onset, atypical progression or diagnostic uncertainty.

6.5 Catatonia

Catatonia can occur with psychiatric or medical illness and may be life-threatening. Document mutism, stupor, posturing, negativism, waxy flexibility, echophenomena, agitation, refusal of food or fluids and autonomic change. Check glucose, electrolytes, renal/liver function, CK, full blood count, infection markers and urine output as clinically indicated. Search for seizures, autoimmune disease, intoxication, withdrawal, medication reactions and malignant catatonia. Escalate urgently if fever, rigidity, autonomic instability, dehydration or raised CK is present.

6.6 Self-harm or suicide risk

A screening tool can structure questioning but cannot replace a compassionate interview. Ask directly about thoughts, intent, plan, access to means, preparations, previous attempts, recent stressors, intoxication, psychosis, agitation, hopelessness, reasons for living, dependants and immediate support. Investigations after an attempt are guided by the method and clinical state: glucose, electrolytes, renal/liver function, pregnancy test where relevant, ECG, paracetamol or other drug levels, toxicology, imaging or surgical assessment. Preserve evidence and involve safeguarding or forensic services when assault or abuse is suspected.

7. Neurodiagnostic investigations

7.1 CT and MRI

Neuroimaging is not required for every patient with depression or an uncomplicated, previously diagnosed psychiatric disorder. Consider urgent CT for head injury, focal neurological deficit, severe sudden headache, seizure, reduced consciousness, suspected intracranial bleeding or raised intracranial pressure. MRI is preferred for many subacute or unexplained neurological presentations because it provides better detail of brain tissue, but availability and emergency stability determine the practical choice.

7.2 EEG

Request or discuss EEG when episodes suggest focal or generalised seizures, unexplained spells, post-ictal confusion, atypical visual or olfactory experiences, rapidly fluctuating awareness or suspected encephalitis. A normal routine EEG does not completely exclude epilepsy; correlate with the event description and consider specialist testing.

7.3 Lumbar puncture

Consider lumbar puncture for suspected meningitis, encephalitis, subarachnoid haemorrhage when appropriate, inflammatory disease or selected autoimmune encephalitis presentations. First assess for contraindications and raised intracranial pressure; obtain urgent senior or specialist advice. Never delay emergency antibiotics or resuscitation while waiting for a routine psychiatric assessment when meningitis or encephalitis is possible.

8. Psychometric and screening instruments

Use a validated tool in the correct language and setting, explain its purpose, record the date and score, and interpret it alongside interview, observation and collateral information.

Using scores safely

• Record the instrument, version, language, date, score and clinical interpretation.
• Ask whether the patient understood each question; use a trained interpreter where needed rather than relying on a child or untrained relative.
• Repeat the same instrument at clinically meaningful intervals rather than several times in one day without a reason.
• Do not use a low score to dismiss concealed risk, psychosis, mania, intoxication, domestic violence or safeguarding concerns.
• Use the score to open a conversation and monitor change, not to replace a diagnosis or determine discharge by itself.

9. Psychosocial investigations: understanding the person in context

Psychosocial assessment is a structured enquiry into the patient’s environment, relationships, resources, stressors, strengths and functioning. It is an investigation because it provides clinically actionable information that cannot be obtained from a blood test.

9.1 Social determinants and practical needs

• Housing stability, overcrowding, homelessness, safety at home and access to clean water and food.
• Income, debt, employment, school, caregiving responsibilities, transport and ability to obtain medicines.
• Health literacy, language, disability, stigma, discrimination, migration, conflict exposure and legal problems.
• Digital access and ability to attend follow-up or use telehealth where offered.

9.2 Family, collateral and support

With consent whenever possible, identify who knows the patient’s baseline, onset, adherence, sleep, substance use, risks, functioning and previous response to treatment. If information must be obtained or shared without consent because of immediate serious risk, use the minimum necessary disclosure, document the legal and ethical basis, and inform the patient when safe.

9.3 Function and recovery

• Activities of daily living: bathing, dressing, eating, continence, medication management and mobility.
• Instrumental activities: finances, shopping, cooking, transport, communication and work or school tasks.
• Relationships, parenting, sexual health, community participation, spiritual life and meaningful roles.
• Strengths, coping strategies, goals, previous successful supports, trusted people and the patient’s own explanation of recovery.

9.4 Substance and trauma assessment

Ask non-judgementally about alcohol, tobacco, cannabis, stimulants, opioids, sedatives, inhalants, khat or other locally used substances, including amount, frequency, route, last use, withdrawal and consequences. Ask about trauma, violence, coercion, exploitation and neglect privately. Avoid forcing detailed trauma disclosure during an acute crisis; prioritise safety, consent, support and referral.

9.5 Capacity, consent and safeguarding

For each important decision, assess whether the person can understand, retain, weigh and communicate the relevant information. Capacity is decision-specific and may fluctuate with delirium, intoxication, severe mood disorder or psychosis. A diagnosis alone does not establish incapacity. Assess children and vulnerable adults for neglect, abuse, exploitation, unsafe caregiving and access to means of harm, following local law and facility policy.

10. A focused investigation plan by setting

11. Documentation template for a psychiatric investigation

12. Worked clinical cases

Case 1: A young adult with first-episode psychosis

A 22-year-old presents with three weeks of voices, suspiciousness and poor sleep. He has no known psychiatric history. He is afebrile, oriented and attentive, but has lost weight and admits using stimulants at parties.

• Immediate questions: glucose, observations, hydration, suicide/violence risk, intoxication/withdrawal and access to weapons or other means.
• Examination: neurological examination, thyroid clues, movement disorder, infection and signs of trauma.
• Targeted tests: full blood count, electrolytes/renal function, calcium, liver function, glucose/HbA1c, thyroid tests, HIV/syphilis according to risk and local policy, pregnancy testing where relevant, urine toxicology if it changes care, ECG and antipsychotic baseline monitoring.
• Escalation: neuroimaging, EEG or specialist autoimmune testing only if atypical features or examination findings support them.
• Psychosocial assessment: housing, family support, education/work, substance pattern, safeguarding, goals and ability to engage with follow-up.

Case 2: An older patient who is suddenly confused

An 80-year-old becomes restless and sees insects in the room two days after admission for pneumonia.

• This is acute, fluctuating and accompanied by impaired attention: treat as possible delirium, not primary psychosis.
• Repeat observations, oxygen saturation and glucose; review medication, pain, constipation, urinary retention and hydration.
• Use 4AT or CAM, obtain collateral baseline and assess infection, renal function, electrolytes, calcium, glucose and oxygenation.
• Escalate for imaging, EEG or lumbar puncture if focal neurology, seizure, meningism, head injury or unexplained reduced consciousness is present.

Case 3: A patient with depression and a new prescription plan

A 35-year-old reports low mood, anhedonia and poor sleep. Before starting medication, ask about past periods of decreased need for sleep, elevated or irritable mood, impulsivity and family history of bipolar disorder. Assess suicide risk directly. Check pregnancy potential, current medicines, alcohol and substances, physical illness and relevant baseline tests. A PHQ-9 can quantify symptoms, but it cannot exclude bipolar disorder, psychosis or medical causes.

Case 4: Monitoring lithium

A patient on lithium develops vomiting and coarse tremor after several days of diarrhoea. Check urgent clinical status, hydration, renal function and electrolytes, and obtain a correctly timed lithium level. Review NSAIDs, ACE inhibitors, diuretics, dehydration and changes in salt intake. Withhold or adjust treatment only under the responsible prescriber’s urgent plan, and escalate severe neurological or cardiac features.

13. Common mistakes and how to prevent them

• Ordering a large panel without a question: define what result will change management before sampling.
• Missing delirium: always ask about acute change, fluctuation, attention and baseline cognition.
• Over-trusting toxicology: detection is not the same as intoxication, causation or impairment.
• Using a score as a diagnosis: interpret tools with history, MSE, examination and collateral information.
• Ignoring medicine safety: obtain metabolic, cardiac, renal, hepatic, pregnancy and movement baselines when relevant.
• Forgetting psychosocial data: a technically normal investigation does not make an unsafe discharge safe.
• Failing to act on results: assign responsibility, communicate critical values and arrange repeat testing.
• Using an interpreter poorly: protect privacy, use a trained interpreter and check understanding.
• Assuming a normal CT excludes serious illness: CT, MRI, EEG and lumbar puncture answer different questions.

14. High-yield examination summary

• Start with safety, ABCDE, observations, glucose and a focused physical/neurological examination.
• Investigations are targeted; most primary psychiatric disorders remain clinical diagnoses.
• New, abrupt, fluctuating, atypical or neurologically accompanied symptoms require a medical and substance-related differential.
• Before psychotropic treatment, consider metabolic, cardiac, renal, hepatic, blood-count, movement, pregnancy and interaction risks.
• Use PHQ-9, GAD-7, AUDIT, C-SSRS, 4AT/CAM, MoCA/MMSE, YMRS, PANSS and WHODAS as structured aids, never as substitutes for clinical judgement.
• Psychosocial investigation includes collateral history, functioning, housing, income, relationships, substances, trauma, safeguarding, capacity, strengths and follow-up access.
• Every result needs interpretation, an action, a responsible person and a review plan.

15. Quick self-test

1. Why is there no single blood test that confirms schizophrenia?
2. Name five bedside assessments that should be performed early in a patient with acute behavioural change.
3. List four red flags that should prompt a medical or neurological work-up for apparent psychosis.
4. What baseline measures are particularly important before antipsychotic treatment?
5. Why can a positive urine toxicology result not by itself prove causation?
6. What are the four core cognitive abilities considered when assessing decision-making capacity?
7. How does a 4AT or CAM support, but not replace, a delirium diagnosis?
8. Which psychosocial findings might make discharge unsafe even when laboratory results are normal?
9. What timing information is essential when interpreting a lithium level?
10. Write one sentence explaining how you would document a critical abnormal result and the action taken.

Answers to the self-test

1. Primary psychiatric disorders are syndromic clinical diagnoses; tests identify mimics, comorbidity and treatment risks rather than proving the label.
2. ABCDE/observations, capillary glucose, oxygen saturation, temperature, level of consciousness/attention, hydration and focused neurological examination are examples.
3. Fluctuating attention or consciousness, fever/autonomic instability, seizure, focal neurology, severe headache, meningism, head injury, abrupt atypical onset, catatonia or immunosuppression are examples.
4. Weight/BMI, waist circumference, pulse, blood pressure, glucose/HbA1c, lipids, movement examination, medication/substance review and ECG when indicated.
5. Tests have detection windows, cross-reactivity and false results; a detected substance may not be active, causal or impairing at that moment.
6. Understanding, retaining, weighing relevant information and communicating a decision.
7. They structure assessment of alertness, cognition, attention and acute change, but clinical judgement, collateral history and repeated assessment remain necessary.
8. Active suicidal intent, violence risk, abuse, homelessness, lack of supervision, inability to obtain medicines, severe substance use or absent follow-up support may make discharge unsafe.
9. The exact time of the last dose and the time the blood sample was taken, along with dose, renal function and symptoms.
10. Record the result and time, who was informed, the interpretation, immediate action, responsible clinician and follow-up/repeat plan.

References and further reading

• World Health Organization. mhGAP guideline for mental, neurological and substance use disorders, 2023.
• World Health Organization. mhGAP Intervention Guide, Version 2.0.
• WHO mhGAP Evidence Centre: self-harm and suicide.
• NICE. Psychosis and schizophrenia in adults: prevention and management.
• NICE. Delirium: prevention, diagnosis and management.
• NICE quality statement: assessing physical health in psychosis and schizophrenia.
• Local Ministry of Health, hospital and medicines-guideline protocols should be followed for test availability, consent, referral, safeguarding and treatment monitoring.