Although the differences between psychoanalysis and psychoanalytically oriented psychotherapy have been the subject of debate for a long time, there is nevertheless a striking lack of systematic empirical studies of extended psychoanalytical treatment. The aim of this thesis is to use empirical evidence to describe similarities and dissimilarities between psychoanalysis and psychoanalytically oriented psychotherapy, as well as the prospects and difficulties inherent in studying the outcomes of these treatments within the framework of a naturalistic quasi-experimental field study.

The thesis builds on five separate studies of the treatments of 405 patients (n=331 in psychotherapy, n=74 in psychoanalysis) with 209 therapists for an average duration of 3.5 years. Patients were surveyed on three occasions with twelve-month intervals to determine symptoms (the Symptom Check List, SCL-90), level of social adjustment (the Social Adjustment Scale, SAS) and 'morale' (the Sense of Coherence Scale, SOCS). The data was analysed in a combined intra-group and inter-group design.

The first study shows small but systematic differences between the patients (n=200) who were referred to psychotherapy and those who were referred to psychoanalysis in respect of socio-demographic and psychiatric characteristics. The second study describes the methodological consequences of the fact that patients seeking psychoanalysis or psychotherapy are hard to control from an experimentalist's point of view. Naturalistic field studies may then be the best way to achieve ecological validity in the study of extended psychoanalytical treatment. The third study shows that the average outcomes of both types of treatment were positive, with effect sizes d=0.4-0.6 for psychotherapy and d=0.4-1.5 for psychoanalysis. In the fourth study, treatment duration and session frequency and long-term outcome had a complex interaction among themselves. Long, high-intensive treatments and short, low-intensive treatments yielded better outcomes than short, intensive treatments and long, low-intensive treatments. The fifth study revealed that patients in psychotherapy who were treated by therapists with orthodox psychoanalytical values showed no positive outcomes from their treatment, at an average. In summary, the long-term differences found between psychoanalysis and psychoanalytically oriented psychotherapy with regard to patients, therapists and outcomes indicate that these treatments differ not only in quantity but also in quality. Long-term follow-up is necessary in studying outcome of long-term psychoanalytically orientedtreatments.