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Cannabis improves night vision: a case study of dark adaptometry and scotopic sensitivity in kif smokers of the Rif mountains of northern Morocco

By July 9, 2004January 14th, 2025No Comments

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E.B. Russoa, , , A. Merzoukib, c, J.Molero Mesab, K.A. Freyd, P.J. Bache

  • a 2235 Wylie Avenue, Missoula, MT 59802, USA
  • b Department of Botany, Faculty of Pharmacy, University of Granada, Granada 18071, Spain
  • c Laboratory of Ethnobotany, Faculty of Sciences, University Abdelmalek Essaadi, Tétouan, Morocco
  • d Montana State University School of Nursing, 236 Corbin Hall, University of Montana, Missoula, MT 59812, USA
  • e Montana Neurobehavioral Specialists, 900 North Orange St., Missoula, MT 59802, USA

Abstract

elsevier-proper-thumbPrevious reports have documented an improvement in night vision among Jamaican fishermen after ingestion of a crude tincture of herbal cannabis, while two members of this group noted that Moroccan fishermen and mountain dwellers observe an analogous improvement after smoking kif, sifted Cannabis sativa mixed with tobacco (Nicotiana rustica). Field-testing of night vision has become possible with a portable device, the LKC Technologies Scotopic Sensitivity Tester-1 (SST-1). This study examines the results of double-blinded graduated THC administration 0–20 mg (as Marinol®) versus placebo in one subject on measures of dark adaptometry and scotopic sensitivity. Analogous field studies were performed in Morocco with the SST-1 in three subjects before and after smoking kif. In both test situations, improvements in night vision measures were noted after THC or cannabis. It is believed that this effect is dose-dependent and cannabinoid-mediated at the retinal level. Further testing may assess possible clinical application of these results in retinitis pigmentosa or other conditions.

Keywords: Cannabis, Medical marijuana, Ethnobotany, Night vision, Ophthalmology, Visual testing

Introduction

Cannabis sativa L. (Cannabaceae) has been utilized in ethnomedicine for millennia. Previous studies have examined its application in Moroccan ethnobotany (Merzouki and Molero Mesa, 1999, Merzouki and Molero Mesa, 2002; Merzouki, 2001), in psychiatry (Russo, 2001a), migraine (Russo, 1998, Russo, 2001b), other pain conditions (Russo, 2002b), and in obstetrics and gynecology (Russo, 2002a).
West reported in 1991 his observations that Jamaican fishermen who smoked or ingested a crude tincture of cannabis were apparently able to see and navigate their boats through dangerous coral reefs in the darkness of night (West, 1991) under conditions that seemed highly improbable. No objective measurements of the subjects were undertaken. Contemporaneously, a similar observation was made in cannabis smokers in Morocco by two members of this group among a population of fishermen with no knowledge of their Jamaican counterparts (Merzouki and Molero Mesa, 1999) (translation from French by EBR):

“Vision: Data were collected during a sojourn effected with the fishermen of the village of Chmaâla (situated on the Mediterranean coast about 100 km east of Tetouan) in July 1991. During our enquiry, one remarked on the particular obscurity of moonless nights and the easy mobility of the fishermen in preparing their launch into the sea. The responses of our informants related the anecdote that they attribute their ability to see [in the dark] to the consumption of kif [Moroccan cannabis mixed with tobacco (Nicotiana rustica)] that they spend entire hours smoking before getting into their barques.”
Claims of cannabis effects on vision are longstanding, but usually negatively oriented, particularly in the Islamic literature. Ibn Sina reported in Book II of his classic, Canon of Medicine, in Persia in the 11th century that cannabis darkened vision (Avicenna, 1294), and this allegation was repeated by al-Ghazzi in Damascus in the 15th century (Hamarneh, 1978) and in a 19th century Afghan love poem (Mathers, 1920). Modern investigation of the phenomenon has been scant, suggesting a decrement in dark adaptation in chronic cannabis smokers in Costa Rica, but not attaining statistical significance (Dawson et al., 1977). In this publication, for the first time, we examine the results of a field study of night vision in cannabis smokers employing objective measures with a scientifically standardized technique.

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Section snippets

Methodology

Objective assessment of night vision has recently become possible with the development of a portable device, the LKC Technologies Scotopic Sensitivity Tester-1 (SST-1; Gathersburg, MD, USA) (Peters et al., 2000), proving comparable in reliability and sensitivity to a standard device. The SST-1 has previously been employed to assess dark adaptation in vitamin A deficiency (Abbott-Johnson et al., 2002, Huerta et al., 2002). Scotopic retinal sensitivity after 30 min dark adaptation has proven to

Results

Results from the single subject double-blind dose escalation THC experiment demonstrated that this individual was able to perceive the stimulus at the lowest instrument setting on the Dark Adaptation Test, irrespective of employed dosage (Fig. 5), creating a “basement” effect, beyond which pharmacological benefit from Marinol could not be demonstrated. In contrast, on the Scotopic Sensitivity Test (Fig. 6), no changes were noted until a decrement in sensitivity was observed at 10 mg, and

Discussion

Although this is a case study, we believe that these results reasonably indicate support of the hypothesis that oral THC and smoked cannabis may improve night vision sufficiently to merit additional investigation. Furthermore, this pharmacological effect appears to be cannabinoid-mediated. In the Jamaican study (West, 1991), it was hypothesized that non-psychoactive cannabis components were responsible for the putative improvement in night vision, and that the sites of action were the

Conclusions

The current study supports the previous ethnobotanical observations that cannabis may improve night vision. This effect seems to be dose-dependent and cannabinoid-mediated. Further study may reveal whether this clinical application of cannabis could be added to treatment of pain, spasticity of multiple sclerosis, and nausea of chemotherapy as recognized indications for this ancient substance.

Acknowledgments

Some financial assistance from the Junta de Andalucia is gratefully acknowledged.

References (31)

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Figures and tables from this article:

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Fig. 1. Field of cannabis growing near Zoumi, Rif Mountains, Morocco, June 2002.
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Fig. 2. High-grade sifted Moroccan cannabis supports combustion.
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Fig. 3. Kif, a Cannabis sativa/Nicotiana rustica mixture in sebsi pipe.
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Fig. 4. Experimental test subject with LKC SST-1 device in background.
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Fig. 5. Dark Adapted Limit (dB) vs. Marinol® dose. No changes are noted as this subject was sufficiently sensitive as to still perceive the stimulus at the lowest instrument setting.
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Fig. 6. Scotopic Sensitivity Limit (dB) vs. Marinol® dose. A decrement in sensitivity is observed at 10 and 20 mg of Marinol. See texts for details.
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Fig. 7. Dark Adaptation Limit (dB) before and after cannabis smoking. A decrement of 1 dB is noted in each subject after smoking kif. This result would be distinctly unlikely due to chance. See text for details.
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Fig. 8. Scotopic Sensitivity Limit (dB) before and after cannabis smoking. A decrement of 1 dB is noted in two subjects and 2 dB in a third subject after smoking kif. This result is statistically significant (P<0.05). See text for details.
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