She took this first analysis very seriously, and could become quite upset if any of her friends criticized psychoanalysis, saying they could only do so if they tried it themselves. The work affected her quite deeply, and some of those who knew her considered that it changed her in many ways. Without it she would probably not have found her way to marriage, nor to the radical ideas that for a time were important to her.

In Stockholm, Karin Boye also became seriously involved with the organization and administration of the Clarté movement, with which she had already come into contact in Uppsala. She also helped to edit the movement's magazine of the same title. The meetings and activities of Clarté , a loosely-organized assembly of some five or six hundred radical intellectuals and political activists from all over Scandinavia, were above all meant to free the minds of its members from the constraints of bourgeois upbringing, education and prejudice. There were two main strands of concern, both of which derived from the movement's central aim of establishing world peace and the happiness of human beings: one focused on the social transformation of the world, and the other was mainly preoccupied with questions of inner transformation by means of psychoanalysis. Among the Swedish members were the poets Gunnar Ekelöf , Nils Ferlin , Harry Martinson, and Karin Boye herself; among lesser-known names were the young poets Stellan Arvidson , Leif Björk , Ingeborg Björklund , Ebbe Linde , Arnold Ljungdal , Erik Mesterton , Ellen Michelsen , Victor Svanberg and Herbert Tingsten . Leif Björk , a young left-wing radical with an interest in psychoanalysis, became Karin Boye's partner, and after some time the couple married. Together with Björk and some other male Clarté members, Karin Boye visited the Soviet Union. It is probable that her experiences there stayed in her subconscious and influenced her in the writing, much later, of her novel about a totalitarian state, Kallocain .

Karin Boye's marriage to Leif Björk did not last long. The couple were too estranged from everyday reality, too over-complicated, and their household economy too precarious for this essentially bourgeois 'social form of love', as Margit Abenius calls it. In addition, it seems to have been more a friendship, or comradeship, than a marriage, and its sexual component was probably not very strong. Karin Boye had already experimented with one extra-marital affair, which brought her a disturbing sense of being hunted by the man for her innermost being. In order to escape having to surrender her inner self, she gave herself to him sexually, in body rather than spirit. These confusions and disturbances grew more frequent after the divorce from Leif Björk , and there were many more opportunities for casual relationships. In 1931 she fell into a severe depression, with suicidal phases. From a friend she obtained the name and address of a psychoanalytic doctor in Berlin.

Her analyst in Berlin, where she moved in January 1932, was Walter Schindler, a Freudian who used techniques of active suggestion. He considered Karin Boye's situation extremely serious, and found her a difficult patient. She herself suffered greatly during the two months of analysis, which came to an end after a crisis. After this, Karin Boye began to be analysed by a woman, Grete Lampl . Of the analysis with Schindler, Scharp noted in his diary that the analyst had said: 'This will end badly. Within ten years she will have taken her own life.'

Apart from analysis, Karin Boye's life in Berlin also involved work. She was an editor of the Swedish avant-garde literary magazine Spektrum , which modelled itself on Eliot's Criterion , and took its name from the idea expressed in one of her poems ('Man's Multiplicity'):

In us a multiplicity lives.
It fumbles towards unity.
Its capturing, gathering burning­glass
we were born to be

Spektrum published the early work of Gunnar Ekelöf , Harry Martinson, Karin Boye and other Swedish modernists; Karin Boye wrote editorials and essays and commissioned work on contemporary European poetry: Erik Mesterton's 'Poetry and Reality in Modern English Lyric Poetry' and 'The Method of T.S. Eliot' first appeared in Spektrum .

Karin Boye also worked as a literary translator, producing a Swedish version of Frieda Uhl's book about Strindberg. Little of this work brought in any money, however, and what with the expense of the psychoanalysis, the poet's financial situation was very precarious. She did, however, manage to see something of Berlin's theatre and café life, moved among male and female homosexuals, witnessed the clashes between extreme left wing and right wing sympathizers, and through Vilhelm Scharp , who knew the Swedish-born Göring , and also Goebbels, gained some insight into the true nature of Nazism. She even attended an election meeting in the Sportpalast at which the Shakespeare-admiring Göring used all his rhetorical skills to outmanoeuvre Hindenburg to Hitler's advantage. It is at this meeting that Karin Boye is reported to have raised her arm in the Hitler salute - not to do so could have cost her her life. Yet there is also some evidence to suggest that she found the mass spectacle fascinating, and that she found some release in surrendering herself to the well-directed and orchestrated cries of 'Die Treue ist der Mark der Ehre '. There is, however, no evidence of her ever having embraced the ideas of Nazism.