Becoming interested in psychopathology under the influence of Georges Dumas, he began to study medicine — alongside such figures as Raymond Aron, Paul Nizan, and Jean-Paul Sartre — as well as psychiatry.
After a training analysis with Rudolph Loewenstein in the thirties, Lagache focused his research interests on Freudian psychoanalysis, bolstered by his knowledge of German; and in 1937 his article on "Mourning, melancholia and mania" enabled him to become a full member of the SPP'[1] — the Paris psychoanalytical society.
After the war, Lagache's views on training came into increasing conflict with those of the society's establishment, as he sought in a liberal synthesis of psychology and psychoanalysis leverage against the medical authoritarianism upheld by Sacha Nacht.
[8] The major problem that had however faced the new Society from the start was that of obtaining recognition from the International Psychoanalytical Association; and here Lacan increasingly appeared as the main obstacle to success.
His little book The Psychoanalysis (1955) was called by Didier Anzieu "a model in terms of accuracy and an example of openness to diversity of fields of application"[citation needed].