Low global frontal brain activity is associated with non-planned or impulsive suicide attempts. A preliminary study

A key element in suicide prevention is the time available to implement effective strategies. Impulsive or unplanned suicide attempts can be defined in function of the generation of a plan or by the duration of the suicidal process, e.g. from the onset of suicidal ideation until suicidal behavior and death. Several factors are considered when assessing the level of planning of suicidal behavior, such as the timing of preparations, isolation from others, presence of help-seeking behavior or suicide notes (Anestis et al., 2014; Beck et al., 1975). The duration of the suicidal process has been characterized in lifetime terms (Neeleman et al., 2004; Runeson et al., 2010), or in function of the most recent suicidal crisis (Deisenhammer et al., 2009; Kattimani et al., 2016; Pearson et al., 2002; Wasserman et al., 2008).

Key elements in the characterization of the suicidal process are the suicide contemplation and suicidal action intervals (Klonsky et al., 2017; Neeleman et al., 2004). By suicide contemplation interval we refer to the time from onset of suicidal ideation to decision to kill oneself. We defined suicidal action interval as the time between the decision to kill oneself and a suicide attempt. Depending on the cut-offs set, 5 min to 7 days, 40–70 % of suicide attempts can be considered impulsive (Kattimani et al., 2016; Pearson et al., 2002; Simon et al., 2001; Williams et al., 1980; Wojnar et al., 2009). Thirty minutes has been established as data supported cut off time to define an impulsive suicide attempt and a proxy of premeditation (Bagge et al., 2013; Conner, 2004; Spokas et al., 2012).

There is limited understanding regarding the neurobiological pathways leading to either impulsive or non-impulsive suicide attempts. Previously we described an association between perception of time slowing and shorter duration of the suicidal process (suicide contemplation and action intervals) (Cáceda et al., 2020). Because of our interest in the mechanisms leading to acute suicidal behavior, we focused on the duration of the immediate pre-attempt phase of the suicidal process. The duration of the suicidal process can be influenced by how an individual processes or judges time, impulsivity, as well as other cognitive factors (Neeleman et al., 2004). For instance, some studies point to cognitive control processes and activity in the paralimbic cortex as crucial differences between impulsive and non-impulsive suicide attempts (Tracy et al., 2015).

EEG is a non-invasive, readily available brain imaging technique and with great time resolution. Different frontal oscillations have been involved cognitive control. For instance, frontomedial cortex theta waves have been linked with novel and difficult stimuli (Cavanagh and Frank, 2014; Huycke et al., 2021). In contrast, alpha power has been associated with both decrease in task-relevant areas, and increase in task-irrelevant areas (Jensen and Mazaheri, 2010). Beta oscillations may be involved in top-down regulation, such as between the frontomedial cortex and the subthalamic nucleus (Zavala et al., 2018), as well as changes in cognitive control over time (Stoll et al., 2016). Lastly frontomedial delta power has also been associated with top-down oscillation inhibition during complex tasks (Harmony, 2013). Previous studies using standard EEG have described alpha, beta and theta frequency abnormalities in patients with current suicidal ideation or with history of suicide attempts (Benschop et al., 2019; Dolsen et al., 2017; Park et al., 2019; Roh et al., 2020). In order to further characterize the neurobiology driving planned and unplanned suicide attempts, we pursued our goal of examining resting state electrical brain activity in individuals within three days of a suicide attempt in relation to the duration of the suicidal process we utilized portable frontal EEG system. We hypothesized that shorter duration of the suicidal process will (unplanned attempts) will positively correlate with lower frontal brain activity.

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