Furthermore, in an open-label 8-week trial using patients with bipolar disorder [42], an open-label 16-week trial using patients with pervasive developmental disorder [43], and a 6-month randomized placebo-controlled trial using patients with pervasive developmental disorder [39], risperidone was found to be beneficial and safe in low doses with no serious side effects in preschoolers; however, these trials reported significant gains in weight and prolactin levels. Here, PRL is linked to pervasive developmental disorder.