Hospitalism (or "anaclitic depression" in its sublethal form) was a pediatric diagnosis used in the 1930s to describe infants who wasted away while in hospital. The symptoms could include retarded physical development, and disruption of perceptual-motor skills and language. It is now understood that this wasting disease was mostly caused by a lack of social contact between the infant and its caregivers. Infants in poorer hospitals were less subject to this disease since those hospitals could not afford incubators which meant that the hospital staff regularly held the infants.

The term was used by the psychotherapist René Spitz in 1945, but its origins are older than this; it occurs in an editorial in "Archives on Pediatrics" as early as 1897.

It appears under adjustment disorders at , in the World Health Organization's classification of diseases, ICD-10.

Disinhibited attachment disorder of childhood (DAD) according to the International Classification of Diseases (ICD-10), is defined as:

Disinhibited attachment disorder is a subtype of the ICD-10 category F94, "Disorders of social functioning with onset specific to childhood and adolescence". The other subtype of F94 is reactive attachment disorder of childhood (RAD – F94 .1).

Synonymous or similar disorders include Affectionless psychopathy and Institutional syndrome.

Within the ICD-10 category scheme, disinhibited attachment disorder specifically excludes Asperger syndrome (F84.5), hospitalism in children (F43.2), and hyperkinetic disorders (F90.-).

In a study by Zeanah, (Zeanah "et al.", 2004) on reactive attachment disorder in maltreated toddlers, the criteria for DSM-IV "disinhibited" RAD (i.e. disinhibited attachment disorder) were:

1. not having a discriminated, preferred attachment figure,

2. not checking back after venturing away from the caregiver,

3. lack of reticence with unfamiliar adults,

4. a willingness to go off with relative strangers.

For comparison, the criteria for DSM-IV "inhibited" RAD were:

1. absence of a discriminated, preferred adult,

2. lack of comfort seeking for distress,

3. failure to respond to comfort when offered,

4. lack of social and emotional reciprocity, and

5. emotion regulation difficulties.

The authors found that these two disorders were not completely independent; a few children may exhibit symptoms of both types of the disorder.