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Dive into the research topics where Marcus Bendtsen is active.

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Featured researches published by Marcus Bendtsen.


British Journal of Psychiatry | 2013

Alcohol assessment and feedback by email for university students: main findings from a randomised controlled trial.

Jim McCambridge; Marcus Bendtsen; Nadine Karlsson; Ian R. White; Per Nilsen; Preben Bendtsen

Background Brief interventions can be efficacious in changing alcohol consumption and increasingly take advantage of the internet to reach high-risk populations such as students. Aims To evaluate the effectiveness of a brief online intervention, controlling for the possible effects of the research process. Method A three-arm parallel groups design was used to explore the magnitude of the feedback and assessment component effects. The three groups were: alcohol assessment and feedback (group 1); alcohol assessment only without feedback (group 2); and no contact, and thus neither assessment nor feedback (group 3). Outcomes were evaluated after 3 months via an invitation to participate in a brief cross-sectional lifestyle survey. The study was undertaken in two universities randomising the email addresses of all 14 910 students (the AMADEUS-1 study, trial registration: ISRCTN28328154). Results Overall, 52% (n = 7809) of students completed follow-up, with small differences in attrition between the three groups. For each of the two primary outcomes, there was one statistically significant difference between groups, with group 1 having 3.7% fewer risky drinkers at follow-up than group 3 (P = 0.006) and group 2 scoring 0.16 points lower than group 3 on the three alcohol consumption questions from the Alcohol Use Disorders Identification Test (AUDIT-C) (P = 0.039). Conclusions This study provides some evidence of population-level benefit attained through intervening with individual students.


Journal of Medical Internet Research | 2012

Effectiveness of a Proactive Mail-Based Alcohol Internet Intervention for University Students: Dismantling the Assessment and Feedback Components in a Randomized Controlled Trial

Preben Bendtsen; Jim McCambridge; Marcus Bendtsen; Nadine Karlsson; Per Nilsen

Background University students in Sweden routinely receive proactive mail-based alcohol Internet interventions sent from student health services. This intervention provides personalized normative feedback on alcohol consumption with suggestions on how to decrease drinking. Earlier feasibility trials by our group and others have examined effectiveness in simple parallel-groups designs. Objective To evaluate the effectiveness of electronic screening and brief intervention, using a randomized controlled trial design that takes account of baseline assessment reactivity (and other possible effects of the research process) due to the similarity between the intervention and assessment content. The design of the study allowed for exploration of the magnitude of the assessment effects per se. Methods This trial used a dismantling design and randomly assigned 5227 students to 3 groups: (1) routine practice assessment and feedback, (2) assessment-only without feedback, and (3) neither assessment nor feedback. At baseline all participants were blinded to study participation, with no contact being made with group 3. We approached students 2 months later to participate in a cross-sectional alcohol survey. All interventions were fully automated and did not have any human involvement. All data used in the analysis were based on self-assessment using questionnaires. The participants were unaware that they were participating in a trial and thus were also blinded to which group they were randomly assigned. Results Overall, 44.69% (n = 2336) of those targeted for study completed follow-up. Attrition was similar in groups 1 (697/1742, 40.01%) and 2 (737/1742, 42.31% retained) and lower in group 3 (902/1743, 51.75% retained). Intention-to-treat analyses among all participants regardless of their baseline drinking status revealed no differences between groups in all alcohol parameters at the 2-month follow-up. Per-protocol analyses of groups 1 and 2 among those who accepted the email intervention (36.2% of the students who were offered the intervention in group 1 and 37.3% of the students in group2 ) and who were risky drinkers at baseline (60.7% follow-up rate in group 1 and 63.5% in group 2) suggested possible small beneficial effects on weekly consumption attributable to feedback. Conclusions This approach to outcome evaluation is highly conservative, and small benefits may follow the actual uptake of feedback intervention in students who are risky drinkers, the precise target group. Trial Registration International Standard Randomized Controlled Trial Number (ISRCTN): 24735383; http://www.controlled-trials.com/ISRCTN24735383 (Archived by WebCite at http://www.webcitation.org/6Awq7gjXG)


Jmir mhealth and uhealth | 2014

Feasibility and user perception of a fully automated push-based multiple-session alcohol intervention for university students: randomized controlled trial

Marcus Bendtsen; Preben Bendtsen

Background In recent years, many electronic health behavior interventions have been developed in order to reach individuals with unhealthy behaviors, such as risky drinking. This is especially relevant for university students, many of whom are risky drinkers. Objective This study explored the acceptability and feasibility in a nontreatment-seeking group of university students (including both risk and nonrisk drinkers), of a fully automated, push-based, multiple-session, alcohol intervention, comparing two modes of delivery by randomizing participants to receive the intervention either by SMS text messaging (short message service, SMS) or by email. Methods A total of 5499 students at Luleå University in northern Sweden were invited to participate in a single-session alcohol assessment and feedback intervention; 28.04% (1542/5499) students completed this part of the study. In total, 29.44% (454/1542) of those participating in the single-session intervention accepted to participate further in the extended multiple-session intervention lasting for 4 weeks. The students were randomized to receive the intervention messages via SMS or email. A follow-up questionnaire was sent immediately after the intervention and 52.9% (240/454) responded. Results No difference was seen regarding satisfaction with the length and frequency of the intervention, regardless of the mode of delivery. Approximately 15% in both the SMS (19/136) and email groups (15/104) would have preferred the other mode of delivery. On the other hand, more students in the SMS group (46/229, 20.1%) stopped participating in the intervention during the 4-week period compared with the email group (10/193, 5.2%). Most students in both groups expressed satisfaction with the content of the messages and would recommend the intervention to a fellow student in need of reducing drinking. A striking difference was seen regarding when a message was read; 88.2% (120/136) of the SMS group read the messages within 1 hour in contrast to 45.2% (47/104) in the email group. In addition, 83.1% (113/136) in the SMS group stated that they read all or almost all the messages, compared with only 63.5% (66/104) in the email group. Conclusions Based on the feedback from the students, an extended, multiple-session, push-based intervention seems to be a feasible option for students interested in additional support after a single-session alcohol intervention. SMS as a mode of delivery seems to have some advantages over email regarding when a message is read and the proportion of messages read. However, more students in the SMS group stopped the intervention than in the email group. Based on these promising findings, further studies comparing the effectiveness of single-session interventions with extended multiple-session interventions delivered separately or in combination are warranted.


Trials | 2012

Alcohol email assessment and feedback study dismantling effectiveness for university students (AMADEUS-1): study protocol for a randomized controlled trial

Jim McCambridge; Preben Bendtsen; Marcus Bendtsen; Per Nilsen

BackgroundAlcohol causes huge problems for population health and for society, which require interventions with individuals as well as populations to prevent and reduce harms. Brief interventions can be effective and increasingly take advantage of the internet to reach high-risk groups such as students. The research literature on the effectiveness of online interventions is developing rapidly and is confronted by methodological challenges common to other areas of e-health including attrition and assessment reactivity and in the design of control conditions.Methods/designThe study aim is to evaluate the effectiveness of a brief online intervention, employing a randomized controlled trial (RCT) design that takes account of baseline assessment reactivity, and other possible effects of the research process. Outcomes will be evaluated after 3 months both among student populations as a whole including for a randomized no contact control group and among those who are risky drinkers randomized to brief assessment and feedback (routine practice) or to brief assessment only. A three-arm parallel groups trial will also allow exploration of the magnitude of the feedback and assessment component effects. The trial will be undertaken simultaneously in 2 universities randomizing approximately 15,300 students who will all be blinded to trial participation. All participants will be offered routine practice intervention at the end of the study.DiscussionThis trial informs the development of routine service delivery in Swedish universities and more broadly contributes a new approach to the study of the effectiveness of online interventions in student populations, with relevance to behaviors other than alcohol consumption. The use of blinding and deception in this study raise ethical issues that warrant further attention.Trial registrationISRCTN28328154


JAMA Internal Medicine | 2016

Effectiveness of Short Message Service Text-Based Smoking Cessation Intervention Among University Students: A Randomized Clinical Trial

Ulrika Müssener; Marcus Bendtsen; Nadine Karlsson; Ian R. White; Jim McCambridge; Preben Bendtsen

IMPORTANCE Smoking is globally the most important preventable cause of ill health and death. Mobile telephone interventions and, in particular, short message service (SMS) text messaging, have the potential to overcome access barriers to traditional health services, not least among young people. OBJECTIVE To determine the effectiveness of a text-based smoking cessation intervention among young people. DESIGN, SETTING, AND PARTICIPANTS A single-blind, 2-arm, randomized clinical trial (Nicotine Exit [NEXit]) was conducted from October 23, 2014, to April 17, 2015; data analysis was performed from April 23, 2014, to May 22, 2015. Participants included daily or weekly smokers willing to set a quit date within 1 month of enrollment. The study used email to invite all college and university students throughout Sweden to participate. INTERVENTIONS The NEXit core program is initiated with a 1- to 4-week motivational phase during which participants can choose to set a stop date. The intervention group then received 157 text messages based on components of effective smoking cessation interventions for 12 weeks. The control group received 1 text every 2 weeks thanking them for participating in the study, with delayed access to the intervention. MAIN OUTCOMES AND MEASURES The primary outcomes were self-reported prolonged abstinence (not having smoked >5 cigarettes over the past 8 weeks) and 4-week point prevalence of complete smoking cessation shortly after the completion of the intervention (approximately 4 months after the quit date). RESULTS A total of 1590 participants, mainly between 21 and 30 years of age, were randomized into the study; 827 (573 [69.3%] women) were allocated to the intervention group and 763 (522 [68.4%] women) were included in the control group. Primary outcome data were available for 783 (94.7%) of the intervention group and 719 (94.2%) of the control group. At baseline, participants were smoking a median (range) of 63 (1-238) and 70 (2-280) cigarettes per week, respectively. Eight-week prolonged abstinence was reported by 203 participants (25.9%) in the intervention group and 105 (14.6%) in the control group; 4-week point prevalence of complete cessation was reported by 161 (20.6%) and 102 (14.2%) participants, respectively, a mean (SD) of 3.9 (0.37) months after the quit date. The adjusted odds ratios (95% CIs) for these findings were 2.05 (1.57-2.67) and 1.56 (1.19-2.05), respectively. CONCLUSIONS AND RELEVANCE With the limitation of assessing only the short-term effect of the intervention, the effects observed in this trial are comparable with those for traditional smoking cessation interventions. The simple NEXit intervention has the potential to improve the uptake of effective smoking cessation interventions. TRIAL REGISTRATION isrctn.org Identifier: ISRCTN75766527.


International Journal of Approximate Reasoning | 2016

Gated Bayesian networks for algorithmic trading

Marcus Bendtsen; Jose M. Peña

This paper introduces a new probabilistic graphical model called gated Bayesian network (GBN). This model evolved from the need to represent processes that include several distinct phases. In essence, a GBN is a model that combines several Bayesian networks (BNs) in such a manner that they may be active or inactive during queries to the model. We use objects called gates to combine BNs, and to activate and deactivate them when predefined logical statements are satisfied. In this paper we also present an algorithm for semi-automatic learning of GBNs. We use the algorithm to learn GBNs that output buy and sell decisions for use in algorithmic trading systems. We show how the learnt GBNs can substantially lower risk towards invested capital, while they at the same time generate similar or better rewards, compared to the benchmark investment strategy buy-and-hold. We also explore some differences and similarities between GBNs and other related formalisms. We present a new probabilistic graphical model which we call gated Bayesian networks.A semi-automatic algorithm is presented that can learn a gated Bayesian network.Gated Bayesian networks are applied to the domain of algorithmic trading.We show that gated Bayesian networks can improve results over a standard benchmark.We compare gated Bayesian networks to other common models and formalisms.


probabilistic graphical models | 2014

Learning Gated Bayesian Networks for Algorithmic Trading

Marcus Bendtsen; Jose M. Peña

Gated Bayesian networks (GBNs) are a recently introduced extension of Bayesian networks that aims to model dynamical systems consisting of several distinct phases. In this paper, we present an algorithm for semi-automatic learning of GBNs. We use the algorithm to learn GBNs that output buy and sell decisions for use in algorithmic trading systems. We show how using the learnt GBNs can substantially lower risks towards invested capital, while at the same time generating similar or better rewards, compared to the benchmark investment strategy buy-and-hold.


Journal of Medical Internet Research | 2015

Online Alcohol Assessment and Feedback for Hazardous and Harmful Drinkers: Findings From the AMADEUS-2 Randomized Controlled Trial of Routine Practice in Swedish Universities

Preben Bendtsen; Marcus Bendtsen; Nadine Karlsson; Ian R. White; Jim McCambridge

Background Previous research on the effectiveness of online alcohol interventions for college students has shown mixed results. Small benefits have been found in some studies and because online interventions are inexpensive and possible to implement on a large scale, there is a need for further study. Objective This study evaluated the effectiveness of national provision of a brief online alcohol intervention for students in Sweden. Methods Risky drinkers at 9 colleges and universities in Sweden were invited by mail and identified using a single screening question. These students (N=1605) gave consent and were randomized into a 2-arm parallel group randomized controlled trial consisting of immediate or delayed access to a fully automated online assessment and intervention with personalized feedback. Results After 2 months, there was no strong evidence of effectiveness with no statistically significant differences in the planned analyses, although there were some indication of possible benefit in sensitivity analyses suggesting an intervention effect of a 10% reduction (95% CI –30% to 10%) in total weekly alcohol consumption. Also, differences in effect sizes between universities were seen with participants from a major university (n=365) reducing their weekly alcohol consumption by 14% (95% CI –23% to –4%). However, lower recruitment than planned and differential attrition in the intervention and control group (49% vs 68%) complicated interpretation of the outcome data. Conclusions Any effects of current national provision are likely to be small and further research and development work is needed to enhance effectiveness. Trial Registration International Standard Randomized Controlled Trial Number (ISRCTN): 02335307; http://www.isrctn.com/ISRCTN02335307 (Archived by WebCite at http://www.webcitation.org/6ZdPUh0R4).


BMC Public Health | 2016

User satisfaction with the structure and content of the NEXit intervention, a text messaging-based smoking cessation programme

Ulrika Müssener; Marcus Bendtsen; Jim McCambridge; Preben Bendtsen

BackgroundSmoking is still the leading cause of preventable ill health and death. There is a limited amount of evidence for effective smoking cessation interventions among young people. To address this, a text messaging-based smoking cessation programme, the NEXit intervention, was developed. Short-term effectiveness, measured immediately after the 12-week intervention revealed that 26% of smokers in the intervention group had prolonged abstinence compared with 15% in the control group. The present study was performed to explore the users’ experiences of the structure and content of the intervention in order to further develop the intervention.MethodsStudents participating in the main NEXit randomized controlled trial were invited to grade their experiences of the structure and content of the intervention after having completed follow-up. The participants received an e-mail with an electronic link to a short questionnaire. Descriptive analysis of the distribution of the responses to the questionnaire was performed. Free-text comments to 14 questions were analysed.ResultsThe response rate for the user feedback questionnaire was 35% (n = 289/827) and 428 free-text comments were collected. The first motivational phase of the intervention was appreciated by 55% (158/289) of the participants. Most participants wanted to quit smoking immediately and only 124/289 (43%) agreed to have to decide a quit-date in the future. Most participants 199/289 (69%) found the content of the messages in the core programme to be very good or good, and the variability between content types was appreciated by 78% (224/289). Only 34% (97/289) of the participants thought that all or nearly all messages were valuable, and some mentioned that it was not really the content that mattered, but that the messages served as a reminder about the decision to quit smoking.ConclusionsThe programme was largely perceived satisfactory in most aspects concerning structure and content by young people and most participants stated that they would recommend it to a friend who wants to quit smoking. The motivational phase might be worth shortening and the number of messages around the quit date itself reduced. Shorter messages seemed to be more acceptable.Trial registrationISRCTN75766527.


Jmir mhealth and uhealth | 2018

Effectiveness of a Text Messaging–Based Intervention Targeting Alcohol Consumption Among University Students: Randomized Controlled Trial

Kristin Thomas; Ulrika Müssener; Catharina Linderoth; Nadine Karlsson; Preben Bendtsen; Marcus Bendtsen

Background Excessive drinking among university students is a global challenge, leading to significant health risks. However, heavy drinking among students is widely accepted and socially normalized. Mobile phone interventions have attempted to reach students who engage in excessive drinking. A growing number of studies suggest that text message–based interventions could potentially reach many students and, if effective, such an intervention might help reduce heavy drinking in the student community. Objective The objective of this study was to test the effectiveness of a behavior change theory–based 6-week text message intervention among university students. Methods This study was a two-arm, randomized controlled trial with an intervention group receiving a 6-week text message intervention and a control group that was referred to treatment as usual at the local student health care center. Outcome measures were collected at baseline and at 3 months after the initial invitation to participate in the intervention. The primary outcome was total weekly alcohol consumption. Secondary outcomes were frequency of heavy episodic drinking, highest estimated blood alcohol concentration, and number of negative consequences attributable to excessive drinking. Results A total of 896 students were randomized to either the intervention or control group. The primary outcome analysis included 92.0% of the participants in the intervention group and 90.1% of the control group. At follow-up, total weekly alcohol consumption decreased in both groups, but no significant between-group difference was seen. Data on the secondary outcomes included 49.1% of the participants in the intervention group and 41.3% of the control group. No significant between-group difference was seen for any of the secondary outcomes. Conclusions The present study was under-powered, which could partly explain the lack of significance. However, the intervention, although theory-based, needs to be re-assessed and refined to better support the target group. Apart from establishing which content forms an effective intervention, the optimal length of an alcohol intervention targeting students also needs to be addressed in future studies. Trial Registration International Standard Randomised Controlled Trial Number ISRCTN95054707; http://www.isrctn.com/ISRCTN95054707 (Archived by WebCite at http://www.webcitation.org/70Ax4vXhd)

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Ian R. White

University College London

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