| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[19] Selective serotonin reuptake inhibitors, oral (duration of therapy – anxiety disorders): Rickels K, Etemad B, Khalid-Khan S, Lohoff FW, Rynn MA, Gallop RJ. Time to relapse after 6 and 12 months' treatment of generalized anxiety disorder with venlafaxine extended release. Arch Gen Psychiatry. 2010 Dec;67(12):1274-81. https://www.ncbi.nlm.nih.gov/pubmed/21135327
Selective serotonin reuptake inhibitors, oral (duration of therapy – anxiety disorders): World Health Organisation. mhGAP intervention guide for mental, neurological and substance use disorders in non-specialized health settings: mental health Gap Action Programme (mhGAP), version 2.0. Geneva, 2016
http://www.who.int/mental_health/mhgap/mhGAP_intervention_guide_02/en/