This book was effectively an abridged version of a report written for the World Health Organisation (1951). Following on from Konrad Lorenz's discovery of imprinting in Geese and other precocial animals, John Bowlby, a psychoanalyst, was asked by the World Health Organisation to look into the effects of separation of infants from mothers.

Bowlby studied the cases of 44 juvenile delinquents. He found that 17 had been separated from mother for some time before the age of 5. This was signifant compared to the control group (also of 44). He concluded that maternal deprivation could seriously effect the child's mental health. He came up with the theory of monotrophy for humans, similar but different to animal imprinting. He proposed that a young infant forms attachment with mother during first 6 months of life. He assumed that the mother-child relationship was qualitatively different to others. Two of his subjects had very little social conscience.  He described this as affectionless psychopathy. Argued that attachment failure resulted in failure to develop social conscience.

'What is believed to be essential for mental health is that the infant and young child should experience a warm, intimate and continuous relationship with his mother (or permanent mother-substitute) in which both find satisfaction and enjoyment'.