Estimation of Multivariate Discrete Hawkes Processes: An Application to Incident Monitoring

Hawkes processes are a class of self-exciting point processes that are used to model complex phenomena. While most applications of Hawkes processes assume that event data occurs in continuous-time, the less-studied discrete-time version of the process is more appropriate in some situations. In this work, we develop methodology for the efficient implementation of discrete Hawkes processes. We achieve this by developing efficient algorithms to evaluate the log-likelihood function and its gradient, whose computational complexity is linear in the number of events. We extend these methods to a particular form of a multivariate marked discrete Hawkes process which we use to model the occurrences of violent events within a forensic psychiatric hospital. A prominent feature of our problem, captured by a mark in our process, is the presence of an alarm system which can be heard throughout the hospital. An alarm is sounded when an event is particularly violent in nature and warrants a call for assistance from other members of staff. We conduct a detailed analysis showing that such a variant of the Hawkes process manages to outperform alternative models in terms of predictive power. Finally, we interpret our findings and describe their implications

Measuring the effects of listening for leisure on outcome after stroke (MELLO):A pilot randomized controlled trial of mindful music listening

Background: Cognitive deficits and low mood are common post-stroke. Music listening is suggested to have beneficial effects on cognition, while mindfulness may improve mood. Combining these approaches may enhance cognitive recovery and improve mood early post-stroke. Aims: To assess the feasibility and acceptability of a novel mindful music listening intervention. Methods: A parallel group randomized controlled feasibility trial with ischemic stroke patients, comparing three groups; mindful music listening, music listening and audiobook listening (control group), eight weeks intervention. Feasibility was measured using adherence to protocol and questionnaires. Cognition (including measures of verbal memory and attention) and mood (Hospital Anxiety and Depression Scale) were assessed at baseline, end of intervention and at six-months post-stroke. Results: Seventy-two participants were randomized to mindful music listening (n = 23), music listening (n = 24), or audiobook listening (n = 25). Feasibility and acceptability measures were encouraging: 94% fully consistent with protocol; 68.1% completing ≥6/8 treatment visits; 80–107% listening adherence; 83% retention to six-month endpoint. Treatment effect sizes for cognition at six month follow-up ranged from d = 0.00 ([−0.64,0.64], music alone), d = 0.31, ([0.36,0.97], mindful music) for list learning; to d = 0.58 ([0.06,1.11], music alone), d = 0.51 ([−0.07,1.09], mindful music) for immediate story recall; and d = 0.67 ([0.12,1.22], music alone), d = 0.77 ([0.16,1.38]mindful music) for attentional switching compared to audiobooks. No signal of change was seen for mood. A definitive study would require 306 participants to detect a clinically substantial difference in improvement (z-score difference = 0.66, p = 0.017, 80% power) in verbal memory (delayed story recall). Conclusions: Mindful music listening is feasible and acceptable post-stroke. Music listening interventions appear to be a promising approach to improving recovery from stroke

Social contagion and environmental predictors of violent and aggressive behaviour

INTRODUCTION: Previous research investigating incidents of violence and aggression (V&A) within secure forensic settings have typically focused on individual factors of patients such as diagnosis and previous engagement in violent behaviour. The current thesis aims to complete an investigation of environmental effects which may influence rates of V&A within secure forensic mental health settings. A systematic review was undertaken to identify, synthesizes and evaluate the available research investigating environmental factors affecting rates of V&A within forensic mental health settings. Secondly an empirical study was completed which investigated the roles of temporal, meteorological and social contagion effects within a high security forensic hospital as they relate to rates of V&A. METHODS: A systemic search of relevant databases identified twenty-two studies meeting the pre-defined search criteria. The results of these studies were synthesised and discussed in the context of four groupings of effects: temporal & seasonal effects; meteorological effects; staff factors and ward characteristics. An assessment of the studies methodological quality was also completed. The empirical paper was a retrospective cohort study which will followed an observational cross-sectional design. Routinely collected data about incidents of V&A were collatedcollected between the dates 26/06/2012 to the 30/09/2021. This data was combined with available meteorological data. Temporal & meteorological effects were investigated using regression models., wWhile social contagion effects were investigated utilising a discreet Hawkes process. RESULTS: The results of the systematic review indicate that environmental effects areis a growing area of research interest which suffers due to inconsistency in the methodological strength of some of the studies. However, there is evidence to support the inclusion of temporal effects, staff factors and ward characteristics into dynamic risk assessments. The need to consider temporal factors was further supported by the results of the empirical study which found a significant day of the week, and time of day effect. These results are discussed in the context of typical routines of the study hospital. There currently exists insufficient evidence to comment fully on the effect of meteorological conditions as they relate to rates of V&A. The application of the Hawkes process provided some tentative evidence to support the theory that incidents of V&A are spread in part by a social contagion effect. CONCLUSION: The current thesis provides good evidence to support the use of the environmental factors within dynamic risk assessments, as there is clear evidence that the risk of V&A is not a constant entity, but instead fluctuates and is influenced by a number of environmental factors. Secondly, it is possible that an environmental effect such as shift change overs, medication distribution or being made aware of previous acts of V&A may be leading to increases in V&A. These findings may be significant in planning future hospital routines and systems to reduce the possible build of environmental pressures

MELLO: Study Protocol: A Feasibility Randomised Controlled Trial Of Listening Based Leisure Activities Following Ischemic Stroke

Background and aims: Stroke is the leading cause of disability in older adults. Early post-stroke interventions often focus on physical recovery. Less attention is paid to mood and cognition enhancing interventions that have the potential to improve well-being without the adverse side effects associated with pharmacological interventions. Daily music listening is an accessible and a low cost activity that has been suggested to have a beneficial effect on cognition and mood post stroke. The mechanism of this effect, or if it is reliable, however is not clear. It is speculated that music listening may enhance control of attention in a similar way to mindfulness interventions, that have been demonstrated to be beneficial in the treatment of mood disorders. This study aims to investigate the feasibility and acceptability of a novel intervention combining music listening with brief mindfulness training, within a randomised controlled trial (RCT) context, early post stroke. Method: This is a three-arm, parallel group, single-blind pilot randomised controlled trial (RCT). Individuals with ischemic stroke undergo assessment of mood and cognition (attention and memory) within four weeks post-stroke prior to being randomised to receive an 8-week music listening, mindful music listening, or audiobook listening intervention. Follow-up assessments of mood and cognition are carried out at 3-months and 6-months post-stroke. In addition, a qualitative interview exploring participants’ experience will be completed post intervention. Conclusions: If the mindful music listening intervention is found to be feasible and acceptable, a full scale RCT to investigate its efficacy would be warranted

MELLO: Study Protocol: A Feasibility Randomised Controlled Trial Of Listening Based Leisure Activities Following Ischemic Stroke

Background and aims: Stroke is the leading cause of disability in older adults. Early post-stroke interventions often focus on physical recovery. Less attention is paid to mood and cognition enhancing interventions that have the potential to improve well-being without the adverse side effects associated with pharmacological interventions. Daily music listening is an accessible and a low cost activity that has been suggested to have a beneficial effect on cognition and mood post stroke. The mechanism of this effect, or if it is reliable, however is not clear. It is speculated that music listening may enhance control of attention in a similar way to mindfulness interventions, that have been demonstrated to be beneficial in the treatment of mood disorders. This study aims to investigate the feasibility and acceptability of a novel intervention combining music listening with brief mindfulness training, within a randomised controlled trial (RCT) context, early post stroke. Method: This is a three-arm, parallel group, single-blind pilot randomised controlled trial (RCT). Individuals with ischemic stroke undergo assessment of mood and cognition (attention and memory) within four weeks post-stroke prior to being randomised to receive an 8-week music listening, mindful music listening, or audiobook listening intervention. Follow-up assessments of mood and cognition are carried out at 3-months and 6-months post-stroke. In addition, a qualitative interview exploring participants’ experience will be completed post intervention. Conclusions: If the mindful music listening intervention is found to be feasible and acceptable, a full scale RCT to investigate its efficacy would be warranted