Psychiatry and clinical psychology are closely related disciplines, and both overlap and affect each other. However, psychiatry is also substantially influenced by more basic psychological theories. Learning theories starting with behavioral concepts have been used for understanding and treating anxiety and addiction, for example. Cognitive theory has had a major impact on treatments for depression and psychosis. Therefore, in this chapter, we will present five psychological theories (psychoanalysis, behaviorism, cognitive theory, social learning, and mindfulness-based concepts) that we regard as historically most influential and useful for psychiatry. In addition, the stress-vulnerability model and the humanistic psychology approach will be outlined. The former provides a general etiological model of almost all psychiatric disorders, whereas the humanistic ideas help conceptualize and establish therapeutic stance and a good client–provider relationship.

Before we can understand the present state of the psychology of religion – with its frequent emphasis on empirical data – it can be helpful to understand the field’s history. The prominent theoreticians that we explore in this chapter – James, Freud, Jung, Maslow, Fromm, Allport, Becker, Frankl, and others – remain influential in the twenty-first century, but they are also controversial. William James’ biography and writings show that debates about religion were never purely intellectual matters for the great scientist and philosopher. Freud’s theorizing on religion is discussed in detail, including his ideas on the origin and meaning of mystical religious experiences, the roots of theistic belief in wish-fulfillment, the notion of religion as a universal obsessional neurosis, and the assessment of the historical importance of religion for civilization. This discussion of Freud is followed by consideration of Carl Jung’s more sympathetic outlook on aspects of religion. The chapter concludes with a comprehensive discussion of the many ways humanistic and existential thinkers have studied religion and spirituality.