Fear conditioning (FC) has been proposed as crucial factor in the etiology and maintenance of panic disorder (PD). This study compared the acquisition of discriminative fear learning between PD patients and healthy subjects (CTR). The main purpose was to test the hypothesis that abnormalities in this process may exist in this population, particularly referred to conditioned responses (CRs) and discriminative fear learning acquisition.

Aversive discriminative conditioning paradigm was administered to 45 patients with a DSM-IV diagnosis of PD with agoraphobia and to 43 healthy subjects. The visual-auditory conditioning paradigm is composed by four visual stimuli as conditioned stimulus (CSs) and a startlingly loud sound as the unconditioned stimulus (US). Only one stimulus (CS+) was followed by the US, instead remainder stimuli were never paired with the US (CS-). The protocol consisted of 3 phases: habituation (HAB), acquisition (ACQ) and extinction (EXT). Skin conductance response (SCR) was used as dependent variable.

During HAB phase no differences were found in response to all stimuli. During ACQ phase, the two groups did not differ in response to CS+; instead patients showed significantly greater reactivity to CS- than controls.

Results suggest equal level of fear acquisition and impaired discriminative fear learning in PD population; moreover discriminative deficit is driven by enhanced safety learning rather than any abnormality in excitatory danger learning. Enhanced responding to CS- among PD may also be interpreted as over-generalization of conditioned fear. Our result have important clinical implication, particularly for behaviour cognitive therapy in Panic Disorder.