Cognitive-behavior therapy (CBT) is considered the "golden standard" psychotherapy for generalized anxiety disorder (GAD). However, it entails different approaches and blanket statements remain hard to formulate. We conducted a randomized controlled trial to compare the most studied CBT protocol for GAD - Borkovec's treatment package - with two other forms : Rational Emotive Behavior Therapy and Acceptance and Commitment Therapy.

The goal of our present study is to compare the most established and studied CBT protocol for GAD, namely Borkovec's treatment package (BTP) with two other forms of CBT: Rational Emotive Behavior Therapy (REBT; Ellis, 1977) and Acceptance and Commitment Therapy (ACT; Hayes et al., 2012). These two forms of therapy were chosen for both conceptual and practical reasons.

At a conceptual level, we wanted to compare forms of CBT with distinct approaches to dysfunctional thoughts. A fundamental postulate of the cognitive model of psychopathology is that the modification of dysfunctional thoughts (i.e., cognitive change) is central to treating psychological disorders, as "all therapies work by altering dysfunctional cognitions, either directly or indirectly". Both classical Beck's cognitive therapy (CT; Beck, 1976), which is an integrated part in Borkovec's GAD treatment package (CT/BTP), and REBT focus on changing dysfunctional thoughts, but they differ fundamentally in their approach to achieving this change. More specifically, Beck's CT focuses primarily on modifying mental representations of relevant circumstances in the forms of dysfunctional descriptions and inferences (i.e., "cold" cognitions: "I will fail."). REBT on the other hand focuses mainly on "hot" cognitions in the form of evaluations/appraisals (i.e., rational and irrational beliefs), which refer to the ways in which "cold" cognitions/ representations are processed in terms of their relevance for personal well-being (i.e., "I must not fail and it is awful if I fail."). In contrast to both CT and REBT, ACT does not directly attempt to modify the content of the thoughts at all, but aims to change the individual's relationship to dysfunctional beliefs (i.e., the significance of having these beliefs), a process through which cognitions are thought to become "neutralized" (i.e., defused) and the anxiety/distress related to them is reduced or accepted.

At a practical level, we wanted to investigate how different forms of CBT (i.e., REBT and ACT/ABBT) would measure up to the established package based on Borkovec's treatment protocol (CT/BTP).

According to REBT, core irrational beliefs (e.g., "I must not fail and it is awful if I fail."), in interaction to various activating events (e.g., a test situation), generate automatic thoughts in the form of descriptions/inferences (e.g., "I will fail here.") that are then further processed by automatic thoughts in the form of specific irrational beliefs derived from the core irrational beliefs (e.g., "I must not fail here and it is awful if I fail here.") that than further generate anxiety symptoms. In its general form, REBT is focused on changing both core beliefs and automatic thoughts, but in its specific form, used here, REBT is focused on changing the core irrational beliefs seen as the fundamental etiopathogenetic mechanisms of GAD.

Inclusion Criteria:

• primary diagnosis of generalized anxiety disorder (GAD)

Exclusion Criteria:

• severe major depression
• bipolar disorder
• panic disorder
• substance use/abuse/dependence
• psychotic disorders
• suicidal or homicidal ideation
• organic brain syndrome
• disabling medical conditions
• mental retardation
• concurrent treatment with psychotropic drug
• psychotherapy outside study