Its place within the anxiety disorders

Adult separation anxiety disorder is characterised by anxiety and fear over separation from people and places to which the patient has a strong attachment. It is associated with clinically significant psychological distress and/or an impairment in functioning, which is not explained by another disorder. The DSM-5 classification locates it within the broad group of anxiety disorders and acknowledges that diagnosis no longer depends on establishing an onset of symptoms during childhood or adolescence. In previous DSM editions, separation anxiety disorder was included within the conditions typically first diagnosed in early life, with the stipulation that symptoms had their onset before the age of 18 years: adults with separation anxiety symptoms could only receive a retrospective diagnosis, based on establishing an onset earlier in life. The ICD-11 takes a broadly similar approach, with the possibility of diagnosing an adult-onset condition (and a recognition that the disorder can occur with or without coexisting panic attacks). The position of separation anxiety disorder within DSM-5 and ICD-11 derives largely from the unanticipated findings of multiple epidemiological studies that indicated a high prevalence of the condition in adults, often in people with an onset of characteristic symptoms after the teenage years.

Differential diagnosis can be difficult

Distinguishing the condition from panic disorder (with or without agoraphobia), generalised anxiety disorder, social anxiety disorder or ‘dependent personality disorder’ is sometimes troublesome.^{Reference Baldwin, Gordon, Abelli and Pini2} The main difference from panic disorder with agoraphobia is that in adult separation anxiety disorder, the primary fear concerns potential separation from others, whereas in panic disorder the primary fear is of having further panic attacks. Distinction from generalised anxiety disorder rests on establishing that the worry about being separated from attachment figures is an isolated concern, rather than just one example of the wide range of troubling worries seen in generalised anxiety disorder. Social phobia is characterised by fear and avoidance of social and performance situations, but individuals with separation anxiety disorder perform well in such situations, providing an attachment figure is visible or held in mind. Separation anxiety disorder is characterised by a narrow range of concerns about the proximity and safety of attachment figures, whereas ‘dependent personality disorder’ manifests through a pervasive and somewhat indiscriminate tendency to rely excessively on others.

World Health Organization mental health surveys involving 18 countries suggest an average lifetime prevalence of separation anxiety disorder in the general population of 4.8%.^{Reference Silove, Alonso, Bromet, Gruber, Samson and Scott3} These surveys suggest a substantial proportion of affected individuals (43.1%) have an onset of symptoms in adulthood; however, meta-analysis indicates that 72.4 and 75% of patients have an onset of illness by 14 and 18 years, respectively.^{Reference Solmi, Radua, Olivola, Croce, Soardo and Salazar de Pablo4} Risk factors for the condition include female gender, reported childhood adversities and lifetime traumatic events; and it impairs social and work functioning markedly, especially in those (more than half of the ‘cases’) with comorbid conditions.^{Reference Shear, Jin, Ruscio, Walters and Kessler5} Adult separation anxiety disorder might be underreported in older adults, but if established in earlier life may become more evident by the unmasking effects of ageing, physical illness, decreased independence and loss of loved ones and other social supports.

Some developments in the understanding of aetiology…

The aetiology of separation anxiety disorder in adults has not been explored extensively, so the potential roles and interactions of environmental, genetic and other factors is unclear. It is associated with the temperament and character dimensions of high ‘harm avoidance’ and low ‘self-directedness’ but is not especially linked to the dimension of ‘intolerance of uncertainty’. Insights from studies of ‘attachment’ in anxious children may not necessarily be relevant to separation anxiety disorder in adults. Anxious attachment and separation anxiety appear highly correlated, but not all individuals with separation anxiety disorder have an insecure attachment style.^{Reference Pini, Abelli, Troisi, Siracusano, Cassano and Shear6} The early but persistent temperamental trait of ‘behavioural inhibition’ is characterised by shyness, withdrawal, avoidance and fears of the unfamiliar, and may be a developmental endophenotype for subsequent development of a range of anxiety disorders. Among adult patients with a primary diagnosis of an affective disorder, separation anxiety symptoms correlate with recollections of difficulties associated with behavioural inhibition.^{Reference Pini, Abelli, Costa, Schiele, Domschke and Baldwin7}

‘Biological’ influences may be important. Variants in the oxytocin receptor, serotonin transporter, opioid receptor µ1, dopamine D4 receptor and translocator protein genes have all been implicated as potential aetiological factors, as has dysregulation of the hypothalamus–pituitary–adrenal axis, dysfunctional cortico-limbic interaction and biased cognitive processing. Hypersensitivity to inhalation of elevated levels of carbon dioxide is an ‘endophenotype’ shared by separation anxiety disorder, panic disorder and anxiety sensitivity.^{Reference Schiele, Bandelow, Baldwin, Pini and Domschke8}

Limited evidence to guide clinical management

Almost nothing is known about optimal approaches to the clinical management of separation anxiety disorder in adults: the efficacy of psychological or pharmacological treatment has barely been studied.^{Reference Bandelow, Allgulander, Baldwin, Costa, Denys and Dilbaz9} In children, psychological treatment studies find some evidence of benefit with cognitive behaviour therapy, parent–child interaction training and ‘summer camp’ programmes, but the findings of randomised placebo-controlled trials of pharmacological treatment provide no convincing evidence of benefit for any medication. The only published randomised placebo-controlled trial of pharmacotherapy in adult separation anxiety disorder was small, exploratory and with a compound that is not available outside North America.

A condition worthy of increased attention

Separation anxiety is a basic fear in humans, most readily observable in children, generally becoming less prominent with age and maturity. Marked, distressing separation anxiety can probably be considered a psychopathological phenomenon, and diagnostic criteria for separation anxiety disorder have benefited from being progressively tightened. The inclusion of separation anxiety disorder within the group of anxiety disorders diagnosable in adults in DSM-5 and ICD-11 should encourage further research into refining its distinctive phenotype and could identify possible endophenotypes that might delineate it from frequently comorbid conditions. Advances in understanding of its clinical features, epidemiology and possible neuropsychobiology suggest that clinicians should not neglect adult separation anxiety disorder, as a condition meriting further investigation. But it seems probable that most clinicians will not yet have enthusiasm for its diagnosis in routine clinical practice, until such time as an evidence-based effective and acceptable treatment has been identified and become widely available.