None listed
Conditions
Brief summary
Long-term cannabis use is associated with deficits in areas of cognitive functioning. It is important to intervene at the cognitive level as cognitive deficits impede everyday functioning (i.e., driving) and health outcomes for individuals who have engaged in prolonged substance use (Aharonovich, Brooks, Nunes, & Hasin, 2008; Cousijn & Filbey, 2015; Sofuoglu, DeVito, Waters, & Carroll, 2013). For example, poor inhibitory control can reduce the ability to refrain from drug use and hence increase the risk of relapse (Goldstein & Volkow, 2002). There is a need to provide cognitive intervention to cannabis users to 1) improve everyday functioning, and 2) alleviate cognitive problems to hopefully empower individuals to cease cannabis. Pharmacological interventions are being investigated for assisting drug abstinence, however, such treatment often has unwanted side effects (e.g., headaches, suicidality) and typically does not result in long-term abstinence (Le Foll, Gorelick, & Goldberg, 2009; Levin et al., 2011; McRae-Clark et al., 2015; Schoedel et al., 2011). Pharmacological interventions at the cognitive level has received less attention and existing studies provide mixed results across populations (Boggs et al., 2018; Hindocha et al., 2018; McGuire et al., 2017; Solowij et al., 2018). Moreover, novel pharmacotherapies can be exorbitantly priced and some have restricted access in Australia. In various reviews, researchers emphasise that effective cognitive-enhancing interventions need to be identified as there are few successful pharmacotherapy options for assisting cognitive problems among people who use substances, such as cannabis (Coles, Kozak, & George, 2018; Cousijn, 2015; Flöel, 2014). Cognitive training has received some attention but with mixed results and researchers are now investigating brain stimulation techniques to target cognitive-related brain regions, such as the dorsolateral prefrontal cortex. The aim of this pilot study is to determine the feasibility of using transcranial Direct Current Stimulation (tDCS; HDCStim, Newronika s.r.l. Italy) to enhance cognitive functioning in individuals who have engaged in long-term, regular cannabis use. We will provide a single session of tDCS (20 minutes, 1.5mA, DLPFC) and measure decision making and inhibitory control before and after tDCS. Urine will also be collected before and after tDCS in order to investigate potential urinary biomarkers (specifically, a panel of amino acids such as glutamine and GABA) of cognition in relation to cannabis use. Our hypothesis is that cognitive functioning, as measured by objective cognitive tests, will increase from pre- to post-tDCS and that changes in urinary biomarkers will be associated with changes in cognitive functioning as a result of tDCS. The group of individuals who use cannabis are expected to show greatest improvements in cognition compared to the control group.
Interventions
Individuals will be screened for eligibility using an online survey. This will include customised questions as well as published measures such as the 21-item Depression, Anxiety, and Stress Scale and Alcohol Use Disorder Identification test.
Using a randomised, double-blind and sham-controlled design, we will compare cognitive outcomes following one session of transcranial Direct Current Stimulation (tDCS; HDCStim, Newronika s.r.l Italy), a brain stimulation paradigm, between individuals who u
Individuals will be screened for eligibility using an online survey. This will include customised questions as well as published measures such as the 21-item Depression, Anxiety, and Stress Scale and Alcohol Use Disorder Identification test. Using a randomised, double-blind and sham-controlled design, we will compare cognitive outcomes following one session of transcranial Direct Current Stimulation (tDCS; HDCStim, Newronika s.r.l Italy), a brain stimulation paradigm, between individuals who use cannabis and a control group of non-drug using individuals. Participants will receive either active or sham/placebo tDCS on one occasion. Active, anodal tDCS will be provided at 1.5mA for 20 minutes. Anodal stimulation will be used to stimulate cortical excitability of the left dorsolateral prefrontal cortex (DLPFC) while cathodal stimulation will be applied to the right DLPFC. Sham stimulation will involve stimulation for 20 seconds and then will automatically switch off. The study also involves: 1) Paired Pulse Transcranial Magnetic Stimulation (TMS). ppTMS (120%) will be applied to the primary motor cortex (M1) once prior to and once after tDCS (within approximately 10 minutes after brain stimulation has been terminated). The pre-tDCS TMS session will take approximately 40 minutes including paradigm set-up. The post-tDCS TMS session will take approximately 20 minutes. During paired pulse TMS two consecutive pulses are applied to the skull with a variable inter-stimulus interval (ISI). Short Interval Intracortical Inhibition (SICI) occurs when a sub-threshold conditioning TMS pulse is given one to five milliseconds before a supra-threshold test pulse. SICI provides a measure of GABA-a (inhibitory neurotransmitter). 2) Urinary biomarker analysis. A urine sample will be collected from participants prior to and shortly after tDCS. 3) Objective cognitive measures. Cognitive function will be measured pre-tDCS and post-tDCS using computerised cognitive tasks. We will use the Iowa Gambling Task (measures decision making) and the Go/No Go task (measures inhibitory control) relevant to dorsolateral prefrontal cortex (DLPFC) functioning. The Go/No Go task also involves a motor component relevant to the primary motor cortex (M1). The cognitive tasks will take approximately 20 minutes to complete. All procedures will be carried out in a Laboratory setting at the University of Tasmania. tDCS will be administered by a registered psychologist with previous experience in brain stimulation paradigms.
Sponsors
University of Tasmania
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Treatment
Masking
Blinded (masking used) (Subject, Caregiver)
Eligibility
Sex/Gender
All
Age
18 Years to 50 Years
Healthy volunteers
Yes
Inclusion criteria
General inclusion criteria: 18-50 years old, male and female, English-speakers, normal or corrected-to-normal vision Cannabis group inclusion criteria: Individuals who have regularly (1+ days per week) used cannabis for 1+ year. We are not specifically recruiting individuals with cannabis use disorder (CUD); however, participants may meet criteria for CUD. Cannabis users will be asked to refrain from cannabis use 24 hours + prior to the Research Session. Control group: No history of cannabis use or minimal (<50 lifetime uses) history of cannabis use
Exclusion criteria
General exclusion criteria: • No current or recent illicit drug use (in the past 30 days) • Dependence on alcohol (a dependency score of 20 or more on the Alcohol Use Disorder Identification Test) or other illicit substances, except nicotine • Pregnancy or suspected pregnancy • Known psychological problems (e.g., depression, anxiety, schizophrenia, PTSD); participants who self-report a clinical diagnosis will be excluded from the study, • Physical conditions or problems (such as cardiac problems and using related medication such as beta-blockers) • Metabolic diseases that would confound measures of metabolites (e.g., renal and kidney disease, phenylketonuria/PKU, tyrosinemia) • Use of prescribed medications to treat psychological conditions (e.g., anxiolytics, antidepressants) due to the potential interactive effect between tDCS and particular medications that could affect measures of cortical excitability Brain stimulation contraindications: • Epilepsy or family history of epilepsy • History of neuropsychiatric conditions (e.g., stroke) • Skin compromised by pre-existing or current burns (e.g., sun burn), injuries, or conditions affecting the scalp (eczema or psoriasis on the head) • Pre-existing implants such as pacemakers and metal implants (excluding dental work such as tooth fillings, dental implants and non-ferromagnetic material). Any implant that is conductive, ferromagnetic or contains other magnetic-sensitive metals such as cochlea implants, stents, or implanted stimulators are contraindicated for TMS • Implanted electronic devices or intracranial magnetic clips such as aneurysm clips • Serious head injury or neurosurgery
Outcome results
None listed