HP appears to be an effective treatment for mild to moderate depression. Several studies have investigated its clinical effects by comparing the Hamilton Depression Rating Scale (HAMD) scores of people taking HP to those of people taking a placebo or commonly prescribed antidepressant drugs. Many of these studies have indicated that HP extracts have a similar clinical response and remission rate to serotonin reuptake inhibitors (SSRIs), while also having a lower rate of treatment discontinuation due to side effects.[1][2][3]
In comparison to tricyclic antidepressants (TCAs), HP appears to have fewer side effects and a lower dropout rate during treatment.[3]
Furthermore, one in vitro study using a specific HP extract (containing only 4 compounds) found that that extract of HP increased neuronal plasticity (the ability of neurons and neural elements to adapt to internal or external stimuli such as chronic stress exposure) and neurogenesis (the formation of new neurons). Additionally, the HP extract exhibited anti-inflammatory properties and protected neurons from cytotoxicity induced by glutamate and N-methyl-D-aspartate (NMDA), which is considered a potential factor in depression.[4]