Although Hamedani et al. (2010) reported that factor V Leiden was associated with a twofold increased risk of arterial ischemic stroke in patients below 50 years of age, Morris et al. (2010), in their analysis of the case-control study of the five most commonly inherited thrombophilias with ischemic stroke: protein C and S deficiencies, antithrombin deficiency, factor V Leiden, and prothrombin gene mutations, found no convincing associations with stroke, even in young patients and patients with patent foramen oval. Here, F5 is linked to thrombophilia.