- History of persistent anxiety despite at least 8 weeks of an adequate (or highest tolerated) dose of anxiolytic pharmacotherapy. This is operationalized to include an antidepressant (e.g., paroxetine 20 mg/d; imipramine 150 mg/d or phenelzine 60 mg/d or their equivalent) or a benzodiazepine (e.g., clonazepam 2 mg/d or its equivalent). The dose of medication should be stable for at least 2 weeks prior to evaluation.