According to Yalom and Leszcz, there are 11 therapeutic factors in group psychotherapy:

1. Instillation of hope

Hope of receiving an effective treatment is a key factor in any therapeutic process. Specifically, in group therapy, not only the therapist but also other group members contribute to the instillation of hope in each patient. 

2. Universality

During group therapy, patients often discover that they are not the only ones experiencing a certain type of psychological distress/suffering. This provides a sense of normality. 

3. Imparting information

By receiving psychoeducational information and explanations of mental health illnesses from either the therapist or group members, each participant can better grasp what they are experiencing.

4. Altruism

When interacting during group therapy, patients often support each other. The possibility of providing help to another person improves the patient's self-esteem.

5. The corrective recapitulation of the primary family group

The similarities between therapy groups and families allow patients to work through early familial conflicts in a corrective fashion.

6. Development of socializing techniques

Through social learning, patients learn about their impact on others. This often results in grasping the discrepancies between what one intends and what one actually does.

7. Imitative behavior

Group members learn not only from the therapist but also from observing how other members, with similar problems, tackle their difficulties.

8. Interpersonal learning

After a certain time, the group becomes a social microcosm for each participant, allowing patients to act out, rather than explain, their dysfunctional interpersonal patterns. In this way, they can receive immediate feedback from both the psychotherapist and other members regarding such behaviors.

9. Group cohesiveness

The therapeutic relationship with the group (therapist included) that each participant develops and the bond they build with the group represent a key factor in the therapeutic process of group therapy.

10. Catharsis

Catharsis refers to the possibility of acknowledging and expressing negative and/or positive feelings towards others.

11. Existential factors

In group therapy, these factors are related to the experience of being human and accepting/facing life in all its aspects, both pleasant and unpleasant.