Similarly, bipolar disorder is characterized by reduced somatostatin cellular density in the caudal entorhinal cortex, diminished numbers of somatostatin-expressing neurons in the hippocampus, and elevated CSF somatostatin levels during manic states, along with decreased somatostatin gene expression in the dorsolateral prefrontal cortex and hippocampus (Lin and Sibille, 2013). This evidence concerns the gene SST and bipolar disorder.