The scientific study of hallucinogenic drugs is challenging; neuroscience has not yet reached the stage where scientists can match your brain-state with what you’re likely to be experiencing. So at the moment, much of the study of hallucinogenic experience is limited to self-reporting. Although scientists can’t control the reporting of subjective experience as much as they can control cells in a petri dish, they can still apply scientific rigour and care to the study of hallucinogenic drugs.

In this two-part blog post, I’m going to compare two papers studying the psychological effects of Salvia divinorum consumption. One is an analysis of self-report questionnaires, and one is a very controlled administration of Salvia to a small group of experienced hallucinogen users. Although in both cases the authors rely on self-reporting to determine the psychological effects of the drug, the latter study has more control over the administration of the drug. Both studies are informative; but which is stronger? Is it better to have a large number of participants, or a large degree of control?

Questionnaire-based study

In this post, I’ll look at Gonzalez et al (2006). Here the authors explore the effects of Salvia divinorum consumption by handing out questionnaires to Salvia users. As well as asking participants to write accounts of their experiences, the questionnaires included several rating scales designed to compare the effects of Salvia to classical psychedelics.

Effects of Salvia

The 32 participants in the study were mostly university students. All subjects had previously smoked Salvia extract, and on average had used Salvia twice. Almost all subjects reported a rapid onset of hallucinogenic effects (within one minute), and most reported the effects lasting between 1 and 15 minutes. When asked to name the best aspects of their experience with Salvia, the most common answers were “entering another reality” and the laughter and happiness that are associated with the trip. As for the negative aspects, the most common answers were the short duration of the effects and the lack of control over the experience. Interestingly, almost half of participants stated that they had experienced negative effects immediately after the trip; however most of these complaints included “tiredness” and “dizziness”, and no-one reported nausea or pain.

Since most of the participants had experience with other drugs, they were then asked to compare the effects of Salvia with others. Most compared Salvia to psilocybin, whilst others found the effects similar to ayahuasca, LSD, ketamine and marijuana. Perhaps as a testament to the unique properties of Salvia, only 44% of participants said they would like to use Salvia regularly.

Figure 1. Many participants report similarities of Salvia to other drugs. In total 20/32 participants reported Salvia as being similar to other drugs. Their responses are shown as percentages. Adapted from Gonzalez et al (2006).

Rating the hallucinogenic experience

The authors then go on to analyse the results of the several hallucinogenic rating scales they employed in their questionnaires. These scales showed that Salvia is typical of classical psychedelics in removing the user from reality and producing intense visual phenomena. The unusual aspect of Salvia was found to be its sedative properties, being more like alcohol than psychedelics in that regard. The authors also note that participants report Salvia causing a loss of control, a unique property for a psychedelic, and the reason why it is often advised to have a sober friend, or “sitter” nearby whilst using Salvia.

According to these rating scales, Salvia does seem to have similarities to the classical psychedelics; however Salvia is unique by causing sedation and a loss of control. The authors infer that the mode of action of Salvia, activating the kappa-opioid receptor, is responsible for these unique properties that accompany the classical psychedelic effects.

In the next blog post, I’ll look at a paper which tries to control the administration of Salvia, and not only relies on self-reporting but also includes some physiological measurements. I’ll compare the results from both studies and see what this tells us about the scientific study of hallucinogens like Salvia divinorum.


Gonzalez D, Riba J, Bouso JC, Gomez-Jarabo G & Barbanoj MJ (2006) Pattern of use and subjective effects of Salvia divinorum among recreational users. Drug and Alcohol Dependence 85:157-162