Survey population
An anonymous, electronic survey (see Supplementary Information) was sent by email on January 17, 2020 to 7607 individuals with PD who had previously engaged with the Parkinson’s Foundation, primarily through attendance of in-person or online educational events or calls to the Foundation’s toll-free Helpline. When the survey closed on February 7, 2020, 1339 surveys had been returned, providing a response rate of 17.6%. Of the returned surveys, 1064 individuals from 49 states had provided complete responses. State representation is shown in Fig. 1. Demographic information about survey respondents can be found in Table 1. Briefly, respondents averaged 71.2 years (±8.3) in age with a mean PD duration of 7.4 years (±6.2). Most (68.5%) respondents held a bachelor’s degree or higher and were currently retired or not employed (87.3%). However, women completing the survey were on average 1.3 years younger than men (70.5 ± 8.5 vs. 71.8 ± 8.2 years; p = 0.02).
Non-users are the majority
We began our survey by asking participants if they had used marijuana or cannabis in the last six months. Most respondents (75.5%, 803/1064) did not report cannabis use within this time frame. Those individuals who identified as non-users were then asked to select up to three reasons for not using cannabis (see Fig. 2). The most frequently identified reasons for non-use included a lack of evidence of the efficacy of cannabis (59.9%, 481/803), a fear of cannabis side effects (34.9%, 280/803) and “other reasons” (31.3%, 250/803), which led to an open text field for respondents to provide additional information. The theme of these open text responses focused on the legality of cannabis (both state and federal), a lack of a need to use cannabis, as well as a disinterest in cannabis overall.
Responses were either pre-identified in the survey as options listed in the category labels or individuals selected “other” and their open text response was analyzed thematically.
We then asked non-users to select up to three reasons that might influence them to consider using marijuana or cannabis. The majority of non-users (76.0%, 610/803) indicated that evidence which supported cannabis use for PD would be most influential in any deliberations to begin cannabis use. Other factors that would also be important in their decision would be if their health team encouraged its use (54.6%, 438/803) or if cannabis side effects were better understood (35.5%, 285/803).
Motivations and routines around Cannabis use
Overall, a quarter of respondents (24.5%, 261/1064) reported they had used cannabis within the previous six months. Age and gender were found to be predictors of cannabis use in this sample (Age OR = 0.95, 95% CI 0.93 to 0.97; Male OR = 1.44, 95% CI 1.03 to 2.03; see Table 2). Cannabis users were younger by an average of 3 years in age than non-users (69 ± 8.6 vs. 72 ± 8.1 years; p < 0.001). When respondents were asked why they used cannabis, the two most common reasons selected were for medical reasons related to their PD only (63.6%, 166/261) or for the combination of both medical and nonmedical (e.g., recreational) reasons (21.5%, 56/261; see Table 3). Age and disease duration were predictors of cannabis use for PD reasons; however, significance disappeared when a provider referral was included in the regression model. For those who used cannabis explicitly for their PD or for both medical and non-medical reasons, about half (46.8%,104/222) indicated they used cannabis for PD symptoms in general and a similar number (43.2%, 96/222) indicated they used cannabis for specific PD symptoms (see Table 3). Comparable findings were identified through thematic analysis of open-text responses. Among the 246 users (85.1%) who reported their cannabis use was for any medical reason or for both medical and non-medical reasons, the most commonly identified reasons for trying cannabis included curiosity (22.8%, 56/246), the idea that cannabis was a natural substance (16.7%, 41/246) and word of mouth (11.4%, 28/246).
We next sought to understand how cannabis users acquired their knowledge about cannabis as a potential therapy (see Table 3). For the majority of users who used cannabis for any medical reason or for both medical and non-medical reasons (excluding recreational users and users who did not know their reason for use), the most common sources of information were from the internet/news (30.5%, 75/246) and from friends or other people with PD (26.0%, 64/246). Most of these users (64.4%, 168/246) had not received a recommendation to use cannabis from a licensed doctor or provider. However, receiving a recommendation from a licensed provider was associated with younger age (OR = 0.95, 95% CI 0.91 to 0.99).
Following up our question on knowledge, we asked these medical users and medical and non-medical users how they learned how to use cannabis (such as dosage, type and frequency of use). We found that a majority of users (56.1%, 138/246) reported that they were not provided any information about recommendations on how to use cannabis. Of the users who were provided information (43.9%, 108/246), the most common sources of information were reported to be a non-PD doctor (25.0%, 27/108), staff at a dispensary (22.2%, 24/108) and friends or other people with PD (22.2%, 24/108).
Among all users, we also sought to better understand the cannabis formulations, strengths and routes of administration they most often used. Two-thirds (64.4%, 168/261) considered themselves “as needed” users and the remainder (35.6%, 93/261) considered themselves “regular” users. Being male, identifying PD as the primary health concern, a shorter disease duration and having been provided a recommendation were all associated with “regular” cannabis use (see Table 4). The daily routine of cannabis use varied and a summary can be found in Table 5. The majority of users reported their time of use at the end of the day, either in the evening (25.3%, 66/261) or at bedtime (26.4%, 69/261, see Fig. 3A).
Each cannabis user was asked (A) when they used cannabis during the day, (B) the primary method by which they used cannabis, (C) where they most often acquired their supply of cannabis, and (D) the type of cannabis they used based on the concentration of the two main constituents: THC (tetrahydrocannabinol) and CBD (cannabinol). The results were further categorized by type of user (n = 261 for all graphs).
Cannabis comes in a number of forms, which can impact how rapidly it is absorbed and for how long it persists in the body19. Users of cannabis most frequently reported spraying or dropping (for example, sublingual drops) (29.1%, 76/261), smoking (27.2%, 71/261) and eating or swallowing (19.2%, 50/261) as their primary method of cannabis use (Fig. 3B). Users acquired cannabis most commonly through a medical dispensary (38.7%, 101/261) or a family member or friend (24.5%, 64/261, see Fig. 3C). When asked details about the type of cannabis used, such as strain of cannabis and concentration of CBD and THC, including high THC, low THC, high CBD, etc., about a quarter of all users did not know (22.2%, 58/261, see Fig. 3D). Of those who did (77.8%, 203/261), almost half did not know the specific type (48.8%, 99/203) or dosage (47.0%, 95/203) they used. Receiving a cannabis recommendation from a licensed provider and identifying as a regular user were associated with knowing the type of cannabis used (OR = 12.2, 95% CI 3.1 to 84.0, and OR = 3.4, 95% CI 1.3 to 12.0, respectively).
Symptom management by cannabis
We asked all users whether they felt that cannabis addressed their motor and non-motor symptoms. A little less than half reported that its use somewhat addressed their motor (41.0%, 107/261) and non-motor symptoms (42.9%, 112/261, see Table 6). There were no differences for reported efficacy between user groups (PD, other medical, nonmedical, etc.). When differentiated between high THC (n = 51) or high/pure CBD (n = 67) users, high THC users reported better efficacy for both motor and nonmotor symptoms (p = 0.02 and p = 0.001, respectively).
Respondents who reported using cannabis for general or for specific PD symptoms (90.1%, 200/261) were also asked about perceived symptom improvement. The most common non-motor symptoms that cannabis users were trying to treat were anxiety (45.5%, 91/200), pain (44.0%, 88/200) and sleep disorders (44.0%, 88/200). The most common motor symptoms that cannabis users were trying to treat included stiffness (43.0%, 86/200) and tremor (42.0%, 84/200). Additional symptom information can be found in Fig. 4. When differentiated between high THC or high/pure CBD users, no differences were found between type of cannabis used and the top selected symptoms for anxiety, pain, sleep disturbances, stiffness and tremor. However, there were differences found between type of cannabis used and the selected symptoms, appetite, dystonia and urinary symptoms, but due to the low selection rates, further analysis was not conducted.
Users that indicated cannabis use for specific or general PD symptoms (n = 200) were asked, “For which of the following symptoms do you use marijuana or cannabis to improve?”.
When asked about associated symptom relief, the majority of these users reported that cannabis use led to a moderate or considerable improvement in the severity of anxiety (78.0%, 71/91), pain (71.6%, 63/88), sleep disorders (76.1%, 67/88), stiffness (64.0%, 55/86), and tremor (63.1%, 53/84). Of those users who selected a slight, moderate or considerable improvement in symptom severity, greater than 80% reported these changes to be meaningful for each of the five symptoms (90.6% anxiety, 89.5% pain, 91.3% sleep disorders, 82.9% stiffness and 84.9% tremor). The majority of these users also reported that cannabis use led to a moderate or considerable improvement in the frequency of anxiety (67.0%, 61/91), pain (63.6%, 56/88), sleep disorders (61.4%, 54/88), stiffness (58.1%, 50/86), and tremor (56.0%, 47/84). Of those users who selected a slight, moderate or considerable improvement in symptom frequency, greater than 80% reported these changes to be meaningful for each of the five symptoms (91.3% anxiety, 87.8% pain, 93.2% sleep disorders, 83.1% stiffness, and 93.9% tremor). Reported improvement can be found in Table 7. When differentiated between high THC or high/pure CBD users, there were no significant differences between groups for reported improvement in severity or frequency for sleep, anxiety, stiffness, or tremor. However, high THC users did report better improvement for pain severity (p = 0.03) compared to high/pure CBD users.
Cannabis user experiences
A small portion of users (12.6% 33/261) reported negative side effects from cannabis use. When differentiated between high THC and high/pure CBD, high THC users were 7.43 times more likely to report side effects than high/pure CBD users (95% CI 1.38 to 59.76). We also polled non-users of cannabis who had indicated a previous negative experience as a reason for not using cannabis in the past six months (4.1%, 33/803). Of these non-users, about half (51.5%, 17/33) also reported negative side effects from cannabis use. These two combined sub-groups most commonly identified anxiety (30.0%, 15/50), impaired coordination (20.0%, 10/50), dizziness (20.0%, 10/50), and “other reasons” (38.0%, 19/50; open text responses included sleepiness, confusion, worsening orthostatic hypotension, etc.) as side effects of cannabis use.
About a quarter of cannabis users (23.0%, 60/261) had stopped using cannabis in the previous six months. Among these users, as well as the subset of non-users who had indicated a previous negative experience (4.1%, 33/803), a lack of symptom improvement (35.5%, 33/93) was the most commonly selected reason for discontinued use (Fig. 5). Identifying as a regular user was inversely associated with cessation (OR = 0.1, 95% CI 0.01 to 0.6). Although high THC users were more likely to report side effects, there were no differences in cessation rates between high THC and high/pure CBD users. Among users who had not discontinued use in the previous six months, the most commonly identified items that cannabis use allowed for included general symptom improvement (40.3%, 81/201), relaxation (14.4%, 29/201), and improvement in daily activities (9.0%, 18/201).
Users and former users (n = 93) responded to the survey question “For what reason did you stop using marijuana or cannabis?” Responses were either pre-identified as one of the survey options or individuals selected “other” and their open text response was analyzed thematically. Lack of symptom improvement was a key reason for halting cannabis use.
Medication satisfaction
All respondents (both users and non-users) reported on their prescription medication use. A few reported not taking medications for PD motor (6.6%, 70/1064) or for non-motor (5.2%, 55/1064) symptoms. Very few (4.6%, 49/1064) were taking no medication at all. Longer disease duration and being male were both inversely associated with being medication free (OR = 0.7, 95% CI 0.5 to 0.9, and OR = 0.1, 95% CI 0.01 to 0.5, respectively). However, those not taking PD prescription medications were no more or less likely to report cannabis usage.
We asked those taking PD medications whether their prescription medications addressed their motor and non-motor symptoms. For motor symptom management, about half (45.3%, 482/1064) reported that medications mostly addressed their symptoms. For non-motor symptom management, a little less than half (41.5%, 441/1064) reported that medications somewhat addressed their symptoms (Table 6). There were no reported differences between users and non-users regarding reported satisfaction for motor symptoms; however, there were significant differences between users and non-users for non-motor symptoms (p = 0.01).
Users rated their prescription medications with higher efficacy than cannabis for control of both motor and non-motor symptoms (p ≪ 0.001 and p = 0.03, respectively).
Among all users, the majority (84.7%, 221/261) reported that cannabis use had no impact on their prescription medication usage, and of the users who had indicated cannabis use for both medical reasons and medical and non-medical reasons, most (89.0%, 219/246) reported that they had not thought that cannabis would be a replacement for their PD prescription medications when they began using.
Clinical trials
We queried all respondents (both users and non-users) about their level of interest in learning about and enrolling in a clinical trial exploring the impact of cannabis on PD symptoms. Most (82.3%, 876/1064) were interested in learning more information about a clinical trial, and more than half (62.3%, 663/1064) were interested in enrolling in a clinical trial. Upon further analysis, interest in clinical trial enrollment was associated with cannabis use, and a longer disease duration (OR = 3.2, 95% CI 2.2 to 4.8, and OR = 1.03, 95% CI 1.01 to 1.06, respectively).
