OCD and trauma-related disorders

Phenomenology of Obsessions vs Compulsions

• Obsessions: Recurrent, persistent, intrusive thoughts, urges, or mental images that cause marked anxiety, distress, or disgust. Common themes include:
  • Contamination: Fears of germs, bodily fluids, toxins, or asbestos.
  • Pathological Doubt & Responsibility for Harm: Dread of failing to lock doors, turn off ovens, or causing catastrophic vehicle collisions.
  • Symmetry & Exactness: Intense need for alignment, precision, or perfection.
  • Taboo Thoughts: Intrusive aggressive, blasphemous, or sexual images that contradict the individual's core moral values (ego-dystonic).
  • The individual attempts to ignore, suppress, or neutralize obsessions with another thought or action.
• Compulsions: Repetitive physical behaviours (handwashing, checking locks, ordering items, tapping) or mental rituals (counting, silent prayer, repeating words silently) that the person feels driven to perform according to rigid rules or in response to an obsession. Compulsions are executed to temporarily reduce the anxiety provoked by the obsession, but are either clearly excessive or not realistically connected to what they are designed to prevent.
• OCD insight: May be good, poor or absent. The presence of intrusive obsessions/compulsions and their course distinguishes OCD; absent insight does not automatically make schizophrenia the diagnosis.

Evidence-Based Treatment Algorithm

• Exposure and Response Prevention (ERP): The gold-standard psychological therapy. Patients create an exposure hierarchy and are systematically exposed to situations that trigger obsessional anxiety (e.g., touching a bathroom handle) while agreeing to refrain completely from performing the compensatory compulsion (e.g., handwashing). Over repeated sessions, neurobiological habituation occurs, breaking the cycle of negative reinforcement.
• High-Dose SSRIs: SSRIs represent first-line pharmacotherapy (fluoxetine, sertraline, fluvoxamine, paroxetine). Critical clinical distinctions for OCD vs depression:
  1. Dosage: OCD requires substantially higher doses than major depressive disorder (e.g., fluoxetine $60\text{ to }80\text{ mg}$ daily, sertraline $200\text{ mg}$ daily).
  2. Latency to Response: Therapeutic response requires a minimum trial duration of 10 to 12 weeks at maximum tolerated doses, compared to 4 to 6 weeks for depression.
• Second-Line Pharmacotherapy:
  • Clomipramine: A tricyclic antidepressant with potent serotonin reuptake inhibition. Highly efficacious in severe refractory OCD, but limited by anticholinergic side effects (dry mouth, constipation, urinary retention), cardiac toxicity (QT prolongation, conduction delay), and seizure risk.
  • Atypical Antipsychotic Augmentation: Adding low-dose aripiprazole ($5\text{ to }10\text{ mg}$) or risperidone ($1\text{ to }2\text{ mg}$) to a maximum-dose SSRI produces clinical response in up to one-third of treatment-resistant cases.

Post-Traumatic Stress Disorder (PTSD) & Acute Stress Disorder

Trauma-related disorders arise following exposure to traumatic events involving death, serious injury, or sexual violence.

Diagnostic Symptom Clusters (DSM-5)

• Criterion A (Trauma Exposure): Exposure to actual or threatened death, serious injury, or sexual violence via: (1) direct experience; (2) witnessing in person; (3) learning that the traumatic event occurred to a close family member or friend; or (4) repeated or extreme exposure to aversive details of traumatic events in occupational duties (e.g., paramedics, police officers, forensic investigators; excluding non-work media/television exposure).
• Four Core Symptom Clusters (persisting for $> 1\text{ month}$):
  1. Intrusion / Re-experiencing Symptoms ($\ge 1$ required): Recurrent, involuntary, distressing memories; traumatic nightmares; dissociative reactions (flashbacks where the individual feels or acts as if the traumatic event is actively recurring); intense psychological distress or physiological reactivity upon exposure to trauma reminders.
  2. Persistent Avoidance ($\ge 1$ required): Deliberate avoidance of internal distressing memories, thoughts, or feelings related to the trauma, or external reminders (people, places, conversations, activities, objects) that trigger memories of the event.
  3. Negative Alterations in Cognitions & Mood ($\ge 2$ required): Inability to recall important aspects of the trauma (dissociative amnesia); persistent distorted blame of self or others; persistent pervasive negative beliefs about oneself or the world ("I am ruined", "The world is entirely evil"); persistent negative emotional state (horror, shame, guilt); marked anhedonia; feelings of detachment or estrangement from loved ones; persistent inability to experience positive emotions.
  4. Alterations in Arousal & Reactivity ($\ge 2$ required): Irritable behaviour and angry outbursts with minimal provocation; reckless or self-destructive behaviour; hypervigilance; exaggerated startle response; concentration impairment; sleep disturbance.

Acute Stress Disorder (ASD) vs PTSD

• Acute stress disorder: Requires at least nine symptoms from a 14-symptom set across intrusion, negative mood, dissociation, avoidance and arousal, lasting three days to one month after qualifying trauma and causing impairment. Its criteria are not identical to PTSD with only a shorter duration.
• Diagnostic Transition: If traumatic stress symptoms persist beyond 1 month (30 days) and cause significant impairment, the diagnosis formally transitions to Post-Traumatic Stress Disorder.

Clinical Management of PTSD & ASD

• Psychotherapy: Recommended First-Line Interventions: Trauma-Focused CBT (TF-CBT); Eye Movement Desensitisation and Reprocessing (EMDR); Non-Recommended / Contraindicated Interventions: Single-Session Critical Incident Stress Debriefing (CISD) (contraindicated; worsens trauma outcomes)

• Pharmacotherapy: Recommended First-Line Interventions: SSRIs (sertraline, paroxetine); SNRIs (venlafaxine); Non-Recommended / Contraindicated Interventions: Benzodiazepines (contraindicated; interferes with fear extinction, worsens PTSD severity)

• Nightmare Rx: Recommended First-Line Interventions: Prazosin (alpha-1 antagonist, dampens central noradrenaline); Non-Recommended / Contraindicated Interventions: Sedating antihistamines or high-dose antipsychotics as routine monotherapy

• Management of Acute Trauma / ASD: Immediate care consists of Psychological First Aid (ensuring physical safety, practical support, comfort, emotional validation, and facilitating natural social support networks). Formal single-session psychological debriefing within 24–72 hours is contraindicated; extensive randomized controlled trials show it interferes with natural emotional processing and increases long-term PTSD rates.

• First-Line Psychotherapy for PTSD: Trauma-Focused CBT (TF-CBT) and Eye Movement Desensitisation and Reprocessing (EMDR). Both facilitate the emotional processing and cognitive reorganization of traumatic memories.

• First-Line Pharmacotherapy: SSRIs (sertraline, paroxetine) and SNRIs (venlafaxine) reduce symptom severity across all four clusters.

• Nightmares: Trauma-focused treatment is central. Prazosin is an off-label, specialist-selected option for troublesome PTSD nightmares with mixed evidence; start cautiously because of postural hypotension. It is not a guaranteed treatment for all PTSD symptoms.

Primary references (checked 7 October 2026): Phoenix Australia trauma guidelines.