Classification & Assessment in Psychiatry · Paper A
Anxiety disorder classification (overview)
ICD-11 reorganised anxiety disorders around shared patterns of fear and avoidance, and moved two conditions out of this category entirely into their own groupings. For example, imagine looking up OCDObsessive-compulsive disorder, a condition of unwanted repeated thoughts and the actions done to relieve them.Read more → in ICD-11 expecting to find it listed alongside generalised anxiety disorder. In practice, OCD has been moved into its own separate grouping, reflecting that its obsessionAn unwanted, intrusive thought, image, or urge that keeps returning and causes distress.Read more →-compulsionA repetitive action or mental act carried out to relieve the anxiety caused by an obsession.Read more → mechanism differs from ordinary anxiety.
Generalised anxiety disorder features diffuse, poorly controlled worry across multiple areas of life, present most days for several months, with no single situational trigger. Panic disorder requires recurrent, unexpected panic attacks not confined to one specific stimulus. Agoraphobia is fear across multiple situations, such as crowds or public transport, driven by fear of difficulty escaping or getting help, distinct from a specific phobia's single trigger. Social anxiety disorder centres on fear of negative evaluation by others. Two important changes from ICD-10: obsessive-compulsive disorder was moved into its own separate grouping, and PTSDPost-traumatic stress disorder, a condition triggered by experiencing or witnessing a traumatic event.Read more → (post-traumatic stress disorder) was moved into a grouping specifically for stress-related disorders, requiring trauma exposure plus a persistent sense of current threat. Say a patient describes recurring intrusive worry across their job, health, and family, with no single trigger and no compulsive ritual. That diffuse, trigger-free worry pattern fits generalised anxiety disorder, not panic disorder or a specific phobia.
Anxiety disorder classification describes how ICD-11 (the World Health Organization's diagnostic manual, now in its 11th edition) and DSM-5 (the American Psychiatric Association's diagnostic manual) sort the different anxiety conditions into distinct diagnoses, rather than treating "anxiety" as one single label.
Both systems group these disorders around a shared core feature: excessive fear (an emotional response to a perceived immediate threat) and anxiety (anticipation of a future threat), together with avoidance of the feared situation. What separates one anxiety disorder from another is the pattern of trigger, course, and associated features layered on top of that shared core.
For example, imagine looking up obsessive-compulsive disorder () in ICD-11, expecting to find it listed alongside generalised anxiety disorder as it once was. In practice, OCD has been moved into its own separate diagnostic grouping, reflecting that its - mechanism differs fundamentally from ordinary anxiety. Older textbooks, and even ICD-10 (the previous edition), still lump OCD and post-traumatic stress disorder () together with anxiety disorders: knowing the current, correct grouping avoids confusion when reading exam questions or current guidance.
The reason the classification keeps changing is that "fear and avoidance" alone is too broad a net: it also describes OCD's and PTSD's hypervigilance. The current systems separate disorders by their underlying mechanism, not just their surface symptom, which is why a diffuse, trigger-independent worry pattern () is treated as fundamentally different from a repetitive, ritual-driven pattern (), even though both can look anxious from the outside.
Generalised anxiety disorder (GAD) features diffuse, poorly controlled worry across multiple areas of life, present most days for several months, with no single situational trigger. Panic disorder requires recurrent, unexpected panic attacks (sudden surges of intense fear with physical symptoms such as palpitations and breathlessness) that are not confined to one specific stimulus. Specific phobia is an intense, persistent fear triggered by one particular object or situation, with the fear clearly out of proportion to any actual danger. Social anxiety disorder centres on fear of negative evaluation by others. Agoraphobia is fear across multiple situations: crowds, open spaces, public transport, driven by fear of difficulty escaping or getting help if something goes wrong, which distinguishes it from a specific phobia's single trigger. Separation anxiety disorder involves excessive fear or anxiety about separation from attachment figures, a diagnosis increasingly recognised in adults as well as children.
Consider a patient with recurring intrusive worry spanning their job, health, and family, with no single identifiable trigger and no compulsive ritual attached: that diffuse, trigger-free worry pattern fits , not panic disorder or a specific phobia. Now imagine a second patient whose fear is confined strictly to flying, with no fear at all in similar situations such as driving; that single, specific trigger fits specific phobia, not agoraphobia's broader pattern. A third patient describing sudden, unprovoked episodes of chest tightness lasting a few minutes, occurring both at home and at work with no clear pattern, fits panic disorder, since the attacks are unexpected rather than confined to one situation. Beyond these within-category mix-ups, the biggest look-alike trap is and themselves: OCD was moved into its own grouping (obsessive-compulsive or related disorders) because (intrusive unwanted thoughts) driving (repetitive behaviours performed to reduce distress) are mechanistically distinct from ordinary fear and avoidance. PTSD was moved into a grouping for disorders associated with stress, requiring exposure to an identifiable traumatic event plus a persistent sense of current threat, re-experiencing symptoms, and avoidance. Neither now counts as an anxiety disorder in ICD-11's structure, even though both can present with anxious symptoms. DSM-5 made a broadly parallel change, so this alignment between the two major systems is itself worth remembering.
Diagnosis rests on a careful clinical history establishing which trigger pattern, course, and associated features are present, since the same core anxiety symptoms can point to several different diagnoses depending on that pattern. Investigations are largely used to exclude organic mimics, for example checking thyroid function to rule out hyperthyroidism presenting with anxiety-like symptoms, rather than to positively confirm an anxiety disorder. Structured screening tools, such as the -7 questionnaire, help quantify symptom severity and track response to treatment over time.
NICE first-line management for most anxiety disorders follows a stepped-care model. Low-intensity psychological interventions come first for milder presentations, escalating to (cognitive behavioural therapy, a structured talking therapy addressing unhelpful thought and behaviour patterns) for moderate to severe cases. Where psychological therapy alone is insufficient, or the patient prefers medication, NICE recommends an (selective serotonin reuptake inhibitor) as first-line pharmacological treatment. For example, consider a patient with moderate who has not improved after a course of low-intensity guided self-help; NICE guidance recommends stepping up to either high-intensity CBT or an SSRI at this point, rather than continuing the same low-intensity approach indefinitely. Getting the specific diagnosis right first is what allows this pathway to be applied correctly, since panic disorder, social anxiety disorder, and specific phobia each have their own recommended CBT protocols even though the overall stepped-care principle is shared.
The single highest-yield trap in this topic is assuming or still count as anxiety disorders because they present with anxious symptoms: in current ICD-11 and DSM-5 classification, both have their own dedicated groupings, and a question that lists "anxiety disorders" as an answer option is testing exactly this.
Anxiety disorders share a fear-anxiety-avoidance core but are told apart by their specific trigger pattern, and and , despite looking anxious, now sit in their own separate diagnostic groupings in both ICD-11 and DSM-5.