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Dive into the research topics where Matthijs Blankers is active.

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Featured researches published by Matthijs Blankers.


PLOS ONE | 2014

Effectiveness of Guided and Unguided Low-Intensity Internet Interventions for Adult Alcohol Misuse: A Meta-Analysis

Heleen Riper; Matthijs Blankers; Hana Hadiwijaya; John A. Cunningham; Stella Clarke; Reinout W. Wiers; David Daniel Ebert; Pim Cuijpers

Background Alcohol misuse ranks within the top ten health conditions with the highest global burden of disease. Low-intensity, Internet interventions for curbing adult alcohol misuse have been shown effective. Few meta-analyses have been carried out, however, and they have involved small numbers of studies, lacked indicators of drinking within low risk guidelines, and examined the effectiveness of unguided self-help only. We therefore conducted a more thorough meta-analysis that included both guided and unguided interventions. Methods Systematic literature searches were performed up to September 2013. Primary outcome was the mean level of alcohol consumption and drinking within low risk guidelines for alcohol consumption at post-treatment. Findings We selected 16 randomised controlled trials (with 23 comparisons and 5,612 participants) for inclusion. Results, showed a small but significant overall effect size in favour of Internet interventions (g = 0.20, 95% CI: 0.13–0.27, p<.001). Participants in Internet interventions drunk on average 22 grams of ethanol less than controls and were significantly more likely to be adhering to low-risk drinking guidelines at post-treatment (RD 0.13, 95% CI: 0.09–0.17, p<.001). Subgroup analyses revealed no significant differences in potential moderators for the outcome of alcohol consumption, although there was a near-significant difference between comparisons with waitlist control and those with assessment-only or alcohol information control conditions (p = .056). Conclusions Internet interventions are effective in reducing adult alcohol consumption and inducing alcohol users to adhere to guidelines for low-risk drinking. This effect is small but from a public health point of view this may warrant large scale implementation at low cost of Internet interventions for adult alcohol misuse. Moderator analyses with sufficient power are, however, needed in order to assess the robustness of these overall results and to assess whether these interventions may impact on subgroups with different levels of success.


Journal of Medical Internet Research | 2010

Missing data approaches in eHealth research: simulation study and a tutorial for nonmathematically inclined researchers.

Matthijs Blankers; Maarten W. J. Koeter; Gerard M. Schippers

Background Missing data is a common nuisance in eHealth research: it is hard to prevent and may invalidate research findings. Objective In this paper several statistical approaches to data “missingness” are discussed and tested in a simulation study. Basic approaches (complete case analysis, mean imputation, and last observation carried forward) and advanced methods (expectation maximization, regression imputation, and multiple imputation) are included in this analysis, and strengths and weaknesses are discussed. Methods The dataset used for the simulation was obtained from a prospective cohort study following participants in an online self-help program for problem drinkers. It contained 124 nonnormally distributed endpoints, that is, daily alcohol consumption counts of the study respondents. Missingness at random (MAR) was induced in a selected variable for 50% of the cases. Validity, reliability, and coverage of the estimates obtained using the different imputation methods were calculated by performing a bootstrapping simulation study. Results In the performed simulation study, the use of multiple imputation techniques led to accurate results. Differences were found between the 4 tested multiple imputation programs: NORM, MICE, Amelia II, and SPSS MI. Among the tested approaches, Amelia II outperformed the others, led to the smallest deviation from the reference value (Cohen’s d = 0.06), and had the largest coverage percentage of the reference confidence interval (96%). Conclusions The use of multiple imputation improves the validity of the results when analyzing datasets with missing observations. Some of the often-used approaches (LOCF, complete cases analysis) did not perform well, and, hence, we recommend not using these. Accumulating support for the analysis of multiple imputed datasets is seen in more recent versions of some of the widely used statistical software programs making the use of multiple imputation more readily available to less mathematically inclined researchers.


Journal of Consulting and Clinical Psychology | 2011

Internet therapy versus internet self-help versus no treatment for problematic alcohol use: A randomized controlled trial.

Matthijs Blankers; Maarten W. J. Koeter; Gerard M. Schippers

OBJECTIVE Problematic alcohol use is the third leading contributor to the global burden of disease, partly because the majority of problem drinkers are not receiving treatment. Internet-based alcohol interventions attract an otherwise untreated population, but their effectiveness has not yet been established. The current study examined the effectiveness of Internet-based therapy (therapy alcohol online; TAO) and Internet-based self-help (self-help alcohol online; SAO) for problematic alcohol users. METHOD Adult problem drinkers (n = 205; 51% female; mean age = 42 years; mean Alcohol Use Disorders Identification Test score = 20) were randomly assigned to TAO, SAO, or an untreated waiting-list control group (WL). Participants in the TAO arm received 7 individual text-based chat-therapy sessions. The TAO and SAO interventions were based on cognitive-behavioral therapy and motivational interviewing techniques. Assessments were given at baseline and 3 and 6 months after randomization. Primary outcome measures were alcohol consumption and treatment response. Secondary outcome measures included measures of quality-of-life. RESULTS Using generalized estimating equation regression models, intention-to-treat analyses demonstrated significant effects for TAO versus WL (p = .002) and for SAO versus WL (p = .03) on alcohol consumption at 3 months postrandomization. Differences between TAO and SAO were not significant at 3 months postrandomization (p = .11) but were significant at 6 months postrandomization (p = .03), with larger effects obtained for TAO. There was a similar pattern of results for treatment response and quality-of-life outcome measures. CONCLUSIONS Results support the effectiveness of cognitive-behavioral therapy/motivational interviewing Internet-based therapy and Internet-based self-help for problematic alcohol users. At 6 months postrandomization, Internet-based therapy led to better results than Internet-based self-help.


Journal of Medical Internet Research | 2011

Modeling the Cost-Effectiveness of Health Care Systems for Alcohol Use Disorders: How Implementation of eHealth Interventions Improves Cost-Effectiveness

Filip Smit; Joran Lokkerbol; Heleen Riper; Maria Cristina Majo; Brigitte Boon; Matthijs Blankers

Background Informing policy decisions about the cost-effectiveness of health care systems (ie, packages of clinical interventions) is probably best done using a modeling approach. To this end, an alcohol model (ALCMOD) was developed. Objective The aim of ALCMOD is to estimate the cost-effectiveness of competing health care systems in curbing alcohol use at the national level. This is illustrated for scenarios where new eHealth technologies for alcohol use disorders are introduced in the Dutch health care system. Method ALCMOD assesses short-term (12-month) incremental cost-effectiveness in terms of reductions in disease burden, that is, disability adjusted life years (DALYs) and health care budget impacts. Results Introduction of new eHealth technologies would substantially increase the cost-effectiveness of the Dutch health care system for alcohol use disorders: every euro spent under the current system returns a value of about the same size (€ 1.08, ie, a “surplus” of 8 euro cents) while the new health care system offers much better returns on investment, that is, every euro spent generates € 1.62 in health-related value. Conclusion Based on the best available evidence, ALCMODs computations suggest that implementation of new eHealth technologies would make the Dutch health care system more cost-effective. This type of information may help (1) to identify opportunities for system innovation, (2) to set agendas for further research, and (3) to inform policy decisions about resource allocation.


Journal of Gambling Studies | 2014

Recommendations for international gambling harm-minimisation guidelines: comparison with effective public health policy

Sally M Gainsbury; Matthijs Blankers; Claire Wilkinson; Karen Schelleman-Offermans; Janna Cousijn

Problem gambling represents a significant public health problem, however, research on effective gambling harm-minimisation measures lags behind other fields, including other addictive disorders. In recognition of the need for consistency between international jurisdictions and the importance of basing policy on empirical evidence, international conventions exist for policy on alcohol, tobacco, and illegal substances. This paper examines the evidence of best practice policies to provide recommendations for international guidelines for harm-minimisation policy for gambling, including specific consideration of the specific requirements for policies on Internet gambling. Evidence indicates that many of the public health policies implemented for addictive substances can be adapted to address gambling-related harms. Specifically, a minimum legal age of at least 18 for gambling participation, licensing of gambling venues and activities with responsible gambling and consumer protection strategies mandated, and brief interventions should be available for those at-risk for and experiencing gambling-related problems. However, there is mixed evidence on the effectiveness of limits on opening hours and gambling venue density and increased taxation to minimise harms. Given increases in trade globalisation and particularly the global nature of Internet gambling, it is recommended that jurisdictions take actions to harmonise gambling public health policies.


Journal of Medical Internet Research | 2012

Economic evaluation of internet-based interventions for harmful alcohol use alongside a pragmatic randomized controlled trial.

Matthijs Blankers; Udo Nabitz; Filip Smit; Maarten W. J. Koeter; Gerard M. Schippers

Background Internet interventions with and without therapist support have been found to be effective treatment options for harmful alcohol users. Internet-based therapy (IT) leads to larger and longer-lasting positive effects than Internet-based self-help (IS), but it is also more costly to provide. Objective To evaluate the cost effectiveness and cost utility of Internet-based interventions for harmful use of alcohol through the assessment of the incremental cost effectiveness of IT compared with IS. Methods This study was performed in a substance abuse treatment center in Amsterdam, the Netherlands. We collected data over the years 2008–2009. A total of 136 participants were included, 70 (51%) were female, and mean age was 41.5 (SD 9.83) years. Reported alcohol consumption and Alcohol Use Disorders Identification Test (AUDIT) scores indicated harmful drinking behavior at baseline. We collected self-reported outcome data prospectively at baseline and 6 months after randomization. Cost data were extracted from the treatment center’s cost records, and sex- and age-specific mean productivity cost data for the Netherlands. Results The median incremental cost-effectiveness ratio was estimated at €3683 per additional treatment responder and €14,710 per quality-adjusted life-year (QALY) gained. At a willingness to pay €20,000 for 1 additional QALY, IT had a 60% likelihood of being more cost effective than IS. Sensitivity analyses attested to the robustness of the findings. Conclusions IT offers better value for money than IS and might therefore be considered as a treatment option, either as first-line treatment in a matched-care approach or as a second-line treatment in the context of a stepped-care approach. Trial Registration Netherlands Trial Register NTR-TC1155; http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=1155 (Archived by WebCite at http://www.webcitation.org/6AqnV4eTU)


International Journal of Behavioral Medicine | 2017

Computer-Based Interventions for Problematic Alcohol Use: a Review of Systematic Reviews

Christopher Sundström; Matthijs Blankers; Zarnie Khadjesari

PurposeThe aim of this review is to provide an overview of knowledge and knowledge gaps in the field of computer-based alcohol interventions by (1) collating evidence on the effectiveness of computer-based alcohol interventions in different populations and (2) exploring the impact of four specified moderators of effectiveness: therapeutic orientation, length of intervention, guidance and trial engagement.MethodsA review of systematic reviews of randomized trials reporting on effectiveness of computer-based alcohol interventions published between 2005 and 2015.ResultsFourteen reviews met the inclusion criteria. Across the included reviews, it was generally reported that computer-based alcohol interventions were effective in reducing alcohol consumption, with mostly small effect sizes. There were indications that longer, multisession interventions are more effective than shorter or single session interventions. Evidence on the association between therapeutic orientation of an intervention, guidance or trial engagement and reductions in alcohol consumption is limited, as the number of reviews addressing these themes is low. None of the included reviews addressed the association between therapeutic orientation, length of intervention or guidance and trial engagement.ConclusionsThis review of systematic reviews highlights the mostly positive evidence supporting computer-based alcohol interventions as well as reveals a number of knowledge gaps that could guide future research in this field.


PLOS ONE | 2011

Substance-related health problems during rave parties in The Netherlands (1997-2008).

Jan Krul; Matthijs Blankers; Armand R. J. Girbes

The objective of this study was to describe a 12-year (1997–2008) observation of substance-related incidents occurring at rave parties in the Netherlands, including length of visits to first-aid stations, substances used, and severity of the incidents. During rave parties, specifically trained medical and paramedical personnel staffed first aid stations. Visitors were diagnosed and treated, and their data were recorded using standardized methods. During the 12-year period with 249 rave parties involving about 3,800,000 visitors, 27,897 people visited a first aid station, of whom 10,100 reported having a substance-related problem. The mean age of these people was 22.3+/−5.4 years; 52.4% of them were male. Most (66.7%) substance-related problems were associated with ecstasy or alcohol use or both. Among 10,100 substance-related cases, 515 required professional medical care, and 16 of these cases were life threatening. People with a substance-related problem stayed 20 min at the first aid station, which was significantly longer than the 5 min that those without a substance-related health problem stayed. These unique data from the Netherlands identify a variety of acute health problems related to the use of alcohol, amphetamines, cannabis, cocaine, ecstasy, and GHB. Although most problems were minor, people using GHB more often required professional medical care those using the other substances. We recommended adherence to harm and risk reduction policy, and the use of first aid stations with specially trained staff for both minor and serious incidents.


Brain Stimulation | 2014

Rebound of affective symptoms following acute cessation of deep brain stimulation in obsessive-compulsive disorder.

Pieter Ooms; Matthijs Blankers; Martijn Figee; Mariska Mantione; Pepijn van den Munckhof; P. Richard Schuurman; Damiaan Denys

BACKGROUND Deep brain stimulation (DBS) is regarded as an effective way to treat refractory obsessive-compulsive disorder (OCD). Little is known about the effects of DBS cessation following a longer period of stimulation. OBJECTIVE To determine the relapse and rebound effects of psychiatric symptoms, and their impact on Quality of Life (QoL) following acute cessation of DBS in OCD patients. METHODS We included 16 out of 32 patients who were treated with DBS between April 2005 and January 2011 at the Academic Medical Center, Amsterdam. After treatment for at least one year, patients entered a 1-week phase in which DBS was switched off. We evaluated psychiatric symptoms and QoL at three time points: before DBS surgery (pre-DBS), following at least one year of DBS treatment (DBS-on) and following 1 week of DBS off (DBS-off). Psychiatric symptoms were assessed with the Yale-Brown obsessive-compulsive disorder scale (Y-BOCS), the Hamilton anxiety rating scale (HAM-A) and the Hamilton depression rating scale (HAM-D). QoL was assessed using the World Health Organization QOL scale (WHOQOL-Bref). RESULTS Switching from DBS-on to DBS-off, Y-BOCS scores increased with 50%, HAM-A scores with 80% and HAM-D scores with 83%. In the DBS-off period, HAM-A and HAM-D scores exceeded pre-surgery levels with approximately 40%, suggesting a rebound phenomenon. Furthermore, a deterioration of physical and psychological QoL to levels comparable with pre-surgery was found during DBS-off. CONCLUSION Acute DBS cessation causes a relapse of obsessions and compulsions and a rebound of anxiety and depression. Additionally, improvements on QoL disappear.


BMC Public Health | 2009

Evaluating real-time internet therapy and online self-help for problematic alcohol consumers: a three-arm RCT protocol

Matthijs Blankers; Maarten W. J. Koeter; Gerard M. Schippers

BackgroundOnly a minority of all alcohol- and drug abusers is receiving professional care. In an attempt to narrow this treatment gap, treatment facilities experiment with online healthcare. Therefore, it is important to test the (cost-)effectiveness of online health interventions in a randomized clinical trial.MethodsThis paper presents the protocol of a three-arm randomized clinical trial to test the (cost-) effectiveness of online treatment for problem drinkers. Self-help online, therapy online and a waiting list are tested against each other. Primary outcome is change in alcohol consumption. Secondary outcome measures include quality of life and working ability. Incremental cost-effectiveness ratios for self-help online alcohol and therapy online alcohol will be calculated. The predictive validity of participant characteristics on treatment adherence and outcome will be explored.DiscussionTo our best knowledge, this randomized clinical trial will be the first to test the effectiveness of therapy online against both self-help online and a waiting-list. It will provide evidence on (cost-) effectiveness of online treatment for problem drinkers and investigate outcome predictors.Trial registrationThis trial is registered in the Dutch Trialregister (Cochrane Collaboration) and traceable as NTR-TC1155.

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Jack Dekker

VU University Amsterdam

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Heleen Riper

VU University Medical Center

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Udo Nabitz

University of Amsterdam

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