Differential diagnosis of major psychiatric conditions

• the following notes outline the main distinguishing features of each condition when entertaining a differential diagnosis. For the full list of diagnostic criteria consult the DSM manual.
• sometimes the diagnosis remains unclear until some further time has elapsed to uncover the full range of symptoms and signs

PSYCHOTIC DISORDERS

Schizophrenia

• delusions PLUS hallucinations PLUS disorganised behaviour PLUS flat/constricted affect
• Impaired function starts prior to age 45
• > 6 months duration
• any affective components occurs after onset of psychotic symptoms and is brief or mild

Schizophreniform disorder

• delusions PLUS hallucinations PLUS disorganised behaviour PLUS flat/constricted affect
• duration < 6 months

Brief reactive psychosis

• delusions PLUS hallucinations PLUS disorganised behaviour PLUS flat/constricted affect
• duration < 2 weeks
• Clear psychosocial triggering event

Schizoaffective disorder

• significant affective components precedes or exceeds psychotic symptoms
• pre-occupation with a mood-congruent delusion or hallucination
• Major Depression with psychotic features
• as above but NOT pre-occupied with mood-congruent delusion and hallucation

ANXIETY DISORDERS

....those related to specific situations

Agoraphobia

• Irrational avoidance of leaving home can occur with or without panic attacks

Social phobia

• Irrational avoidance of social situations for fear of humiliation (still able to leave home)

Simple phobia

• Irrational avoidance of specific objects or situations (but not in regard to leaving home or being placed in social situations)

.....those not related to specific trigger

Panic disorder

• Recurrent episodes of panic attacks

Obsessive-compulsive disorder

• Associated with obsessions or compulsions

Generalised anxiety disorder

• Chronic, persistent anxiety symptoms
• Post-traumatic stress disorder
• Recurrent re-experience of previous traumatic event

Adjustment disorder with depressed mood

• Anxiety symptoms
• Clear psychosocial triggering event < 3 months prior

MOOD DISORDERS

Major depression

• Episodes of depression syndrome > 2 weeks BUT < 2 years duration

Bipolar affective disorderer

• Episodes of depression syndrome > 2 weeks BUT < 2 years duration PLUS manic episodes

Dysthymic disorder

• Episodes of depressed mood > 2 years duration

Cyclothymic disorder

• Episodes of depressed mood > 2 years duration PLUS manic episodes

Adjustment disorder with depressed mood

• Episodes of depressed mood > 2 years duration Clear psychosocial stressor triggering event < 3 months prior

Features that may distinguish delerium (from psychosis)

• Fluctuating or depressed conscious state
• Tactile or visual hallucinations (vs auditory)
• Abnormal vital signs or diaphoresis
• Specific neurological symptoms or signs - headache, focal neurological deficit, inco-ordination
• Identifiable acute medical illness

GLOSSARY

• Psychosis - a condition resulting in loss of reality testing and insight
• Neurosis - a condition with chronic or recurrent anxiety and preserved reality testing and insight
• Reality testing - the objective evaluation and judgment of the outside world
• Thought disorder - a disturbance characterised by loosened associations, neologism and illogical constructs
• Loosening of associations - flow of thought (or speech) with constantly shifting ideas of no clear connection
• Illogical thinking - thinking containing erroneous conclusions and internal constructs and inconsistent with intellectual and cultural background
• Neologism - novel words created by the patient
• Hallucination - false sensory perception not associated with real external stimuli
• Delusion - fixed false beliefs based on incorrect inference about external reality not correctable with reasoning and inconsistent with intellectual and cultural background
• Mood-incongruent delusion/hallucination - mood incongruous with the content of the thought or perception e.g. depressed mood with elevated thoughts.
• Anxiety - feeling of apprehension
• Panic attack - an acute severe anxiety attack
• Depersonalisation - feeling of unreality, strangeness, or altered identity (not feeling part of your body, 'floating or standing outside of my body watching in')
• Derealisation - feeling that the environment has changed ('not connected to the world as if standing behind a window and cut off')
• Obsession - persistent, recurrent ideas or impulses that are consciously acknowledged as irrational
• Compulsions - recurrent, compelling acts that develop in an attempt to relieve obsessions or anxiety
• Depressive syndrome - a feeling of sadness, loneliness, dejection, or hopelessness associated with
• Manic syndrome - flight of ideas, elated or grandiose mood and psychomotor excitement
• Flight of ideas - rapid, continuous speech with constantly shifting and loosely connected ideas
• Organic brain syndrome - any physical condition that temporarily (delirium) or permanantly (dementia) affects brain function
• Delirium - acute disturbance in affect, orientation, memory, and consciousness
• Dementia - chronic deterioration in intellectual and emotional function (consciousness usually preserved initially)

Above derived from DSM diagnostic algorithms