DSM-5 Definition of RAD
The DSM-5 gives the following criteria for Reactive Attachment Disorder:
Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)

A. A Consistent Pattern of inhibited, emotionally withdrawn behavior toward adult caregivers, manifested by both of the following:
The child rarely or minimally seeks comfort when distressed
The child rarely or minimally responds to comfort when distressed

B. A persistent social or emotional disturbance characterized by at least two of the following:
Minimal social or emotional responsiveness to others
Limited positive affect
Episodes of unexplained irritability, sadness, of fearfulness that are evident even during nonthreatening interactions with adult caregivers

C. The child has experienced a pattern of extremes of insufficient care as evidenced by at least one of the following:​
Social neglect or deprivation in the form of persistent lack of having basic emotional needs for comfort, stimulation, and affection met by caring adults
Repeated changes of primary caregivers that limit opportunities to form stable attachments (eg: frequent changes in foster care)
Rearing in unusual settings that severely limit opportunities to form selective attachments (eg: institutions with high child to caregiver ratios)

D. The care in Criterion C is presumed to be responsible for the disturbed behavior in Criterion A (eg: the disturbances in Criterion A began following the lack of adequate care in Criterion C)

E. The criteria are not met for Autism Spectrum Disorder

F. The disturbance is evident before age 5 years

G. The child has a developmental age of at least 9 months
Specify if Persistent: The disorder has been present for more than 12 months
Specify current severity: Reactive Attachment Disorder is specified as severe when a child exhibits all symptoms of the disorder, with each symptom manifesting at relatively high levels