In humans, the dose response to THC is biphasic with regard to anxiety and anxiety-like behavior. That is, at low to moderate doses, THC elicits anxiolytic effects, whereas at high doses it has anxiogenic effects (D'Souza et al., 2004; Gonzalez, 2007). In the present studies, although THC caused a decrease in marble burying at 0.3 mg/kg, this effect was not dose-related. Higher doses (i.e., 10 and 30 mg/kg), which reduced marble burying behavior, also lead to profound hypomotility, indicating sedation, as reported previously (Martin et al., 1987). Previously, Onaivi et al. (1990) reported that THC produced dose-related, anxiogenic-like effects in both mice and rats, as assessed in the elevated plus maze test. The marble burying test, however, is not designed to assess increased anxiogenic-like behavior.
