Introduction

Murder-suicide, homicide-suicide, and dyadic death (later indicated as HS) are phrases used to indicate a situation where a perpetrator kills at least one victim and then commits suicide [1,2,3]. To represent an actual HS, the homicide(s) (H) and suicide (S) must occur within a time frame which is not consistently described in the literature: for some authors the time elapsed between the H and S should be no longer than 24 h, while others adopt as inclusion criterion also a several days time frame, up to a week, and still others do not use a timeline at all [4,5,6,7,8,9,10,11,12,13].

Theoretical understanding of the HS phenomenon from a psychological perspective proposes two main positions: the event is considered essentially homicidal by the first, with suicide being a concomitant event likely due to remorse, while the second position maintains that HS is essentially a two-staged suicide, extended to the perpetrator’s intimates [10, 11, 14,15,16,17,18,19,20]. Besides, other authors have suggested that HS is a distinct phenomenon from both H and S [21, 22].

Some classification models have been proposed for HS. The model by Marzuk and coworkers (1992) [10], later modified by Hanzlick & Koponen (1994) [23], discriminates among five types of HS, based on type (the relationship between victim and offender) and class (principal offenders’ motive or precipitating factor) [10, 23]. According to type, the most common type of domestic homicide and the most prevalent in overall HS cases is the killing of an intimate partner followed by suicide [9, 10, 24,25,26,27,28,29]. Marzuk (1992) proposes two motives for spousal or intimate partner HS: revenge and declining health [10]. The typology proposed by Harper and Voigt (2007) includes intimate or domestic lethal violence as the most common type of HS [30]. This is usually perpetrated by older male offenders, unemployed, with the victim being a current or former spouse or partner; furthermore, in older, middle-class offenders (aged also more than 75 years), the motive underlying HS is likely declining health, leading to the so-called mercy killing-suicide.

Briefly, while it is widely acknowledged that most HS happen in the context of an intimate partner relationship, data about this relatively rare phenomenon worldwide are still scant and overall poorly systematized. Therefore, the aim of this mini-review is to focus on this topic, assessing the research papers published since 2012.

Methods

We performed a review of the literature about HS and intimate partner violence, published from January 2012 to June 2018, with full text available and written in English. Moreover, we excluded book chapters, editorials, letters to the editor, and case reports. We searched articles in Pubmed and Scopus using the search strings reported in Appendix 1. Six of the authors (C.G., S.D.M., C.G., C.C., L.L., M.M.) reviewed and screened articles eligible according to the PRISMA (Preferred Reporting Items for Systematic Reviews and MetaAnalyses) flow diagram [31]. Article screening was based on title first, then on the abstract, and eventually on the full-text, to exclude those that were clearly not relevant to the review topic. Any disagreement among reviewers was resolved through group discussion. Additional records identified through other sources, such as the reference list of the papers included through database searching, were added.

Finally, each reviewer extracted and tabulated the following information from each article: perpetrators’ and victims’ age, gender, race/ethnicity, marital status or victim-perpetrator relationship, socio-economic, educational, employment status; cause of death for both H and S; autopsy findings, including toxicology; alcohol/drug consumption; health status, medical history; psychiatric symptoms/ diagnosis/treatment; previous suicide attempts; motive and latent motive for HS; evidence of prior threats to kill, history of domestic abuse; previous criminal history; and suicide notes.

Results

The selection process of the articles is shown in Fig. 1; 12 articles were identified through database search and 10 from other sources, so we eventually examined 22 articles. The included studies are grouped according to the Country where they were performed and summarized below. For an overview and more details see Table 1.

Fig. 1
figure 1

PRISMA flow diagram and search strings. The diagram shows the process of the article selection

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Table 1 Results
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USA Studies

The largest study was performed by Reckdenwald [37] and included 1073 intimate partner HS (current intimate N = 868, former intimate N = 172) out of 1718 HS cases in the 10-year period from 2003 to 2013. Most HS happened in White couples; most perpetrators were males (94.87%), and most victims were females (94.32%). The method was shooting in 80.62% of cases; wound location and number were also specified in this study, which anyway did not report about HS motives.

Salari [36] reported about 718 intimate partner HS in the period 1999–2005 and provided details about primary homicidal (48%) or suicidal (27%) ideation. Moreover, the Salari study compared elderly and young couples: mercy killings were more common in the first and breakup-related HS in the latter; moreover, elderly perpetrators showed a greater frequency of suicidal ideation, while homicidal ideation was more frequent in younger ones. Suicidal ideation in the elderly was related not only to mental or physical health problems and caregiver burden but also to financial problems and debts. In 25% of cases, a primary homicidal or suicidal intent was not reported. Shooting was the most commonly used method (88%).

The study by Bridges [32] compared two groups between 1968 and 1975, one of 400 elderly H victims and one of 184 elderly HS, the latter including 122 intimate partner HS. The authors report that 81% of victims were elderly females, albeit specific information was unavailable either for perpetrators’ features or motives for the cases of elderly HS. One or both partners of a long-living marriage having multiple health problems was identified as risk factor for HS, likely suggesting mercy killing/altruistic suicide, with shooting as the most common method (81.8%).

Smucker [38] reported about 202 HS cases in North Carolina from 2004 to 2013, but this study did not provide details either about motives leading to HS or about victims’ features. Information about perpetrators was limited to gender (N = 193 males, N = 9 females). Method for HS was shooting in most cases, and a higher risk to commit suicide after homicide was described in those cases when a firearm was used (OR = 2.68) or the perpetrator was married to the victim (OR = 2.36, compared with other types of relationships).

Burgess [33] described 165 HS cases from 2001 to 2011. More than half of perpetrators were males, while most victims were females and younger than their partners. A minority of perpetrators had a history of convictions, either drug- and alcohol-related or due to violent offense. The main reasons for HS were domestic conflict and consortial, related to physical ailing. Ethnic differences were found regarding methods for HS, with gunshot and blunt force trauma being more frequent among Caucasians perpetrators and cutting instrument injuries being more common in African American, Hispanic, and Asian perpetrators.

In the Richards study [35], 36% of the 83 HS cases assessed from 2002 to 2009 were the evolution of a history of domestic violence; shooting was the method used in 92% of cases. Only few details were described for perpetrators and victims (e.g., relationship between perpetrator and victim, age).

Manning [15] focused on educational level in a sample of 20 HS from 2005 to 2008 and argued that the proportion of H ending with an S was greater when the perpetrator was less educated than the victim, while S was least likely to happen when the perpetrator was more educated than the victim. In the Manning study, all perpetrators were male, and all victims were female; loss of intimacy was the main reason for HS, and shooting was the most common method for HS.

Oliffe [34] described 7 HS cases reported by newspaper articles from 1987 to 2013. All perpetrators were male, and all victims were female. Reasons included financial stress in 6 cases out of 7; mental and physical health and relationship stress were also mentioned as motives for HS. Shooting was the most common method both for H and S (4/7 cases).

European studies

Cengija [39] described 17 HS cases in Croatia from 1986 to 2009, 76% of which were spousal/consortial. This study did not discriminate between HS subtypes. Overall, most perpetrators were males (82%) (only two females killed their spouses), and most victims were females (74%), all belonging to a low socioeconomic class. Amorous jealousy was the most common cause of these events (35%), and firearm was the most common method both for H (50%) and S (65%).

The De Koning study [1], performed in Belgium, included 47 HS cases from 1935 to 2010 and grouped according to offenders’ and victims’ age (less or more than 55 years). While no significant difference was found between the two groups of “young” and “old” offenders and victims regarding gender (most perpetrators were male and most victims female), differences emerged in motive for HS, being mostly amorous jealousy in offenders aged less than 55 and mercy killing/altruistic suicide in most cases of offenders aged more than 55 years. Differences were found in method as well: it was usually shooting both for victim and perpetrator in couples aged less than 55 and shooting for the victim but asphyxia for the perpetrator in those aged more than 55 years.

A different approach of subgrouping HS was adopted by Gregory [40] in the UK. The 22 HS cases recorded in the period 1993–2007 were subdivided according to the presence/absence of a history of domestic abuse. Most perpetrators were male, except for one female in the group with a history of domestic abuse, and all victims were female in the group with no known history of domestic abuse. The main reason underlying HS was jealousy or the partner attempting to leave the relationship in both subgroups. No predominant method for H and S was identified.

Nearly two thirds of the 60 HS cases included in the Flynn study [41], performed in England and Wales in the period 2006–2008, were intimate partner HS involving current or former spouse or partner. This study reported detailed information also about perpetrators’ previous history of domestic violence, self-harming behaviors (including suicide attempts), and bereavement by suicide; moreover, it described prevalence of mental health disorder diagnosis or previous contact with mental health services. Classification of HS offenders discriminated between those with a history of depression and those with a history of domestic violence. Main motives for HS were described as falling in one of the following two categories: loss of a close personal relationship either through imminent separation or divorce and a significant change in the relationship due to victim’s health conditions (e.g., dementia). Overall, most offenders were middle-aged males; 56 were registered with a general practitioner practice, and suicidal ideation was noted by a general practitioner in 7 cases. The majority had no previous contact with mental health services.

Panczak [22] studied 63 intimate partner HS out of 73 total cases of HS in Switzerland in the period from 1990 to 2008. This study described detailed information about perpetrators (mostly males) and victims (including not only gender, age, marital and occupational status but also nationality, residence status, religion, education, living conditions, number of persons per room, language, urbanization), but did not discriminate among HS subtypes and did not assess motives for HS. Regarding the method, shooting was the most common one for both H and S.

Two studies were performed in Germany [42, 43]. The first, by Siems [42], involved 58 HS, including 13 cases of failed HS from 1994 to 2014. Sixty-six percent of these cases were intimate partner HS involving married couples (N = 33) or ex-partners (N = 5). Considering all the events, the main motives reported were financial problems and breakup conflicts. Most perpetrators were males (93%), and most victims were females (76%). Shooting was the method for 57% of H and 52% of S. In 95% of cases, H and S occurred on the same day. The Weeke study [43] reported about 288 events, of which only 29 H and S acts were completed. Only familial HS cases were considered, where perpetrator killed family members or intimate current or former partners from 1996 to 2005. Most offenders were males (N = 256). This study specifically assessed suicide notes, reporting that 40% of males committing uxoricides left suicide notes, while only 28.6% of female offenders did so. Uxoricide-suicide perpetrators who wrote notes often had underage children and seemed to feel a greater urge to explain their acts.

The study by Verzeletti [44] included 19 HS in Brescia (Italy) from 1987 to 2012. All the victims were females, related to their male perpetrators by an intimate binding (wife, girlfriend, ex-girlfriend, lover, daughter), which was an intimate partner relationship in 18 cases. Overall, 6/19 events were related to the breakup of a relationship and 4/10 to morbid jealousy, while 4/19 happened in couples with one partner suffering of a severe illness. Both perpetrators and victims had a low educational level. Method was shooting in most cases, both for H (13/19) and S (16/19). Perpetrators committed S just after the H in all the events except one, in which S occurred the day after the H.

The Sturup and Caman study [45] included 8 intimate partner HS cases out of a total of 13 HS cases recorded in Sweden in the period from 2007 to 2009. The authors described HS type according to the models proposed by Liem (2010) and Harper and Voigt (2007) [21, 30], respectively. According to the first, they classified these 8 cases as intimate partner HS, with one further described as intimate partner HS related to declining health. According to the latter model, they classified 7 cases as domestic HS and one as mercy killing-suicide. All perpetrators were males while all victims were females; shooting was the main method both for H and S.

Balica [46] reported about 83 HS cases in Romania in the period 2002–2013; 69% of these were classified as intimate partner HS. The Balica study did not describe HS methods but had a specific focus on the effect of emigration: intimate partner HS were significantly more frequent in the emigrant than in the non-emigrant sample (p < 0.04). Overall, most perpetrators were males, with a low occupational status in 48.3% of cases, while victims were mainly females. Reasons underlying HS included end of relationship/divorce, jealously, suspicion of unfaithfulness/infidelity, and financial difficulties.

Comparison USA/Sweden

The study by Regoeczi [47] compared 176 cases, including all types of HS in the USA and Sweden; intimate partner HS were 59.4% of cases in the USA and 54.3% of cases in Sweden. The main motive for intimate partner HS was a maladaptive stress reaction in cases of divorce or interpersonal crisis. Perpetrators in both countries were mostly males, while victims were mostly females. Differences between the two countries were found in methods for HS (shooting in 95% of cases in the USA and 39% of cases in Sweden) and in history of domestic violence, which was reported in 51.9% of cases in the USA and in 10.5% of HS cases in Sweden.

Other countries

Satoh [48] reported about 76 HS cases in Japan from 1999 to 2011, including all types of HS. Details about intimate partner HS were not specified in this study. The mixed nature of the sample and the fact that in 63.2% of cases the perpetrator/victim relationship was a parent/children one, explain why perpetrators were males in 49.3% of cases and females in the remaining 50.7%. Motives for HS were reported only in 40% of the cases. The most frequent method for HS in the total sample was asphyxia, via hanging for S (43%) and strangulation for H (41.1%). Suicide notes were left in 42.1% of cases.

The Densley study [49] was performed in China about 63 total cases of HS from 2000 to 2014, 38% of which were motivated by intimate partner conflict and 12.5% by extra-marital affair. Intimate partner violence was the most prevalent risk factor for HS. Most perpetrators were male and most victims were female. In most H cases, the weapon used was a knife, while methods for S were highly variable, including use of a knife, drug, or poison in more than half of cases.

In Ghana, Adinkrah [50] described 36 intimate partner HS out of a total of 50 cases of HS from 1990 to 2009. Main reasons included sexual jealously, partner being sexually unfaithful, infidelity, end of the relationships and quarrels, but neither number of cases nor percentages were specified. Perpetrators were males in 97.2%, and victims were females in 97.2%. The method for HS was in most cases the use of a firearm, both for H (62.9%) and S (51.4%).

Discussion

The number of available studies about the topic of intimate partner HS is scant, and their heterogeneity makes it difficult to generalize or compare results. Most studies reported data about mixed HS samples including different types of HS and not specifically focused on the intimate partner subtype, making it hard or impossible to disentangle the features of each HS subtype. Moreover, another relevant problem with studies in the HS field is that they do not report the same type of data; therefore, the information we decided to extract from the available studies (see Methods) was often missing about several variables.

Countries and Sample Size

Most studies were performed in European countries (10/22, 46%) (Germany, N = 2, UK N = 2, Italy N = 1, Switzerland N = 1, Belgium N = 1, Croatia N = 1, Romania N = 1, Sweden N = 1) [1, 22, 39,40,41,42,43,44,45,46] and in the USA (8/22, 36%) [15, 32, 33, 34•, 35, 36••, 37, 38]. One study was a comparative analysis involving both the USA and Sweden (1/22, 4.5%) [47]. One of the selected studies was conducted in China (1/22, 4.5%) [49], one in Japan (1/22, 4.5%) [48], and one in Ghana (1/22, 4.5%) [50].

Overall, the studies included in this mini-review assessed nearly 3900 HS cases, with almost 2700 involving an intimate partner (about 70%).

Period Assessed

The time period assessed by the studies highly varied, spanning from a minimum of 2 years [41, 45] to a maximum of 75 years [1]. The oldest data available were from 1935 in the De Koning’s study [1], while the most recent ones were from 2014 [42•].

Type of Study and Data Source

All studies were retrospective. Panczak’s study was described as a cohort study, but actually HS-related information was retrospectively assessed [22]. We found one newspaper article review [34•]; one comparative analysis [47], one short report [44], and two case series [41, 45].

Most of the studies took information from multiple sources (41%). Overall, sources most frequently used were medical examiners records/forensic or legal medicine archives (13/22, 59%) [1, 15, 33, 37,38,39,40,41, 42•, 44, 45, 47, 48] and newspapers/online archives (9/22, 41%) [1, 34•, 35, 36••, 39, 43, 46, 49, 50]; followed by public security (police, FBI, etc.) reports and court judgment records (7/22, 32%) [32, 38, 39, 41, 46, 47, 49]. Specific datasets on domestic violence were used only in two out of 22 studies (1%) [15, 35], and only a couple of studies retrieved information from statistic institutes or census data (2/22, 1%) [22, 39].

Studies relied on information retrieved from different sources, some of which are available only in specific countries (for instance datasets on domestic violence, or census data). In several countries, for example Romania [46], there is no standardized reporting system for HS, so newspapers and online archives become the main sources for data in these cases.

HS Rate

HS rate was reported by nearly a half of the studies (10/22, 45%) [22, 39,40,41, 44,45,46,47,48, 50]. See Table 2 for more details.

Table 2 HS rate
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The HS rate was quite variable, ranging from 0.01 per 100,000 persons per year in Ghana [50] to 0.2 per 100,000 in Croatia and Cuyahoga County [46, 47]. The literature reports a relatively high HS rate in the USA, ranging from 0.27 per year in Kentucky to 0.38 per 100,000 persons per year in central Virginia [7, 51].

Perpetrators’ and Victims’ Features

Different studies showed highly various information about perpetrators and victims. Some papers limited the description to gender and age: 21/22 studies studies (95%) described a consistently higher prevalence of male offenders, and 20/22 studies (90%) reported a prevalence of females among victims. Perpetrators’ age was reported by 19/22 studies (86%), while victims’ age by 18/22 studies (82%). Some studies offered more detailed information, including race/ethnicity (6/22, 27%) [15, 32, 33, 37, 40, 41]; marital status or victim-perpetrator relationship (19/22, 86%) [15, 22, 32, 33, 34•, 35, 36••, 37, 39,40,41, 42•, 44,45,46, 48,49,50]; socio-economic and employment status (10/22, 45%) [22, 33, 39,40,41, 42•, 44,45,46, 50]; educational level (4/22, 18%) [15, 22, 39, 46]; autopsy findings (3/22, 14%) [37, 42•, 44]; including toxicology; alcohol/drug consumption (11/22, 50%) [1, 33, 36••, 39,40,41, 42•, 44,45,46,47]; health status and medical history, including psychiatric symptoms/diagnosis/treatment and previous suicide attempts (12/22, 54%) [1, 33, 36••, 39,40,41, 42•, 43,44,45,46,47]; history of domestic abuse (7/22, 32%) [15, 33, 35, 40, 41, 46, 47], and previous criminal history (2/22, 9%) [33, 40].

The main results emerging from the current mini-review are consistent with previous reports about intimate partner HS, suggesting that intimate partner HS are predominantly committed by men, usually married, cohabiting or recently separated from their partner, with a medium or low employment status, while the victim is usually the female current or former partner [2]. An association between HS and socially disadvantaged conditions, unemployment, educational level, and legal problems/previous convictions has been suggested by all but one author [37].

Mental illness has sometimes been reported in offenders, with depression as the most commonly cited disorder [26, 52]. The Sturup and Caman’s study, which is one of the 11/22 studies (50%) reporting details about contact with mental health services and psychiatric morbidity [1, 36••, 39,40,41, 42•, 44, 46,47,48], offered an interesting perspective about this issue, suggesting that it was not necessarily a risk factor for HS. In fact, only few HS cases were perpetrated by people affected by a diagnosed mental disorder.

Motives for HS

Based on motives for HS, some studies adopted exclusion criteria: for instance, Manning and coworkers (2014) limited their analysis to HS cases that were rooted in conflict or hostility, counting cases in which the killing followed an argument, separation, or divorce; in which the killer had recently threatened or complained about the victim; and in which suicide notes suggested that the killer was angry with the victim [15]. Other studies included all intimate partner HS and then subdivided them according to the reasons underlying the behavior. Finally, in some studies, data about motives were not specified (5/22, 23%) [22, 35, 37, 38, 43].

Two main intimate partner HS categories have been suggested in the literature: the first is focused on a pathological type of possessiveness or jealously, usually occurring in HS with perpetrators or victims aged 55 years or less, whereas the latter usually involves an elderly couple with at least one severely ill partner (“mercy killing”), with offender and victim aged more than 55 years [4, 10]. Briefly, these can be described as amorous jealousy/domestic conflict and mercy killing/altruistic suicide. Ten out of 22 studies (45%) reported only jealously/domestic conflict as motive for HS [15, 39,40,41, 42•, 45,46,47, 49, 50], while 7/22 (32%) reported both Marzuk’s motives [1, 32, 33, 34•, 36••, 44, 48].

Some studies also focused on other trigger factors for HS, such as social stressors and financial difficulties [1, 33, 34•, 36••, 42•, 46, 48]. The role of mental health is debated: some papers suggested a relationship between mental health status and HS [34•, 39, 46, 48], while others described mental health status as an influencing factor [41]. Mental health problems observed in HS events were depression and substance/alcohol abuse in most cases [34•, 47].

Timing

The high variability in time elapsed between H and S is a shared feature of the overall HS literature, and currently there seems to be no specific relation between differences in time elapsed between H and S and perpetrator’s and victim’s profile or motives leading to the HS event. Some researchers rely on a time span of 24 h [24] or several days [5], between the H and the S of the perpetrator; others use a week as an inclusion criterion [5] and still others do not use a timeline at all [12].

In the present review, time between H and S was analyzed in 14 studies (63%). Studies that chose 24-h time frame as a maximum to define the event as HS were 23% [1, 15, 37, 43, 47]; in 41%, the cutoff was longer [22, 39,40,41, 42•, 44, 46, 49, 50]; in most cases, 1 week as a maximum value, even if the suicidal events almost always occurred in the first 24 h. Finally, in 32% of the studies, this information was not specified [32, 33, 34•, 35, 36••, 38, 48].

Prior Threat to Kill

Information about prior threat to kill the victim was not specified in nearly a half of the studies assessed (9/22, 41%) [1, 22, 32, 34•, 37,38,39, 44, 48]. Seven studies (7/22, 32%) reported prior threats to kill: these were described but not specifically quantified by Burgess (2015) and Adinkrah (2014), while Balica (2016) and Manning (2014) gave more information about number of cases with prior threats (respectively, two cases of prior death threats and one case in which the perpetrator threated S before committing the H; eight cases, 40% of the sample) [15, 33, 46, 50]. Siems (2017) specified how 24% of the offenders announced their plan prior to the event (farewell letter or announcement by telephone call; call to the ambulance service or police after the H) [42•]. Weeke (2017) reported an evidence of planning in 59% of cases in which the perpetrator left a suicide note. In some studies, prior threat to kill was not assessed, but it was reported the association between HS and previous domestic violence (7/22, 32%) [43]. Gregory (2012) mentioned one case out of 12 of domestic abuse where there was a prior threat to kill the victim [40]. Regoeczi and coworkers (2016) reported only a history of previous domestic violence [47], as Richards and coworkers (2014) who described that in 36% of the cases HS was the evolution of domestic violence [35]. Previous episodes of domestic violence were reported by Manning (2014), Burgess (2015), and Flynn (2016; for 39% of the offenders) [15, 33, 41]. In Salari (2015), threats to victim and prior history of domestic violence were found, in particular among young and middle-aged couples in which perpetrators had primary homicidal intention (48% of cases) [36••].

Suicide Notes

Information about suicide notes was available for about half of the studies (10/22, 45%) [1, 15, 33, 34•, 36••, 39, 40, 42•, 43, 48]. Interestingly, the study reporting the higher percentage of suicide notes left by the perpetrator was the one performed in Japan by Satoh (2016), where suicide notes were left in 42.1% of cases [48]. Weeke et al. (2017) specifically focused on the comparison between suicide notes writers and no-writers of suicide notes; but consistently with the literature, they failed to find any specific difference between the two groups [43]. Overall, the results suggest that the most significant predicting factor for writing suicide notes is having an underage children; no difference has been found between male and female offenders [43].

Method for HS

The current mini-review is consistent with the existing literature in reporting shooting as the most common method for HS [3, 26, 53,54,55,56,57,58]. In 16/22 (73%) of the selected studies, perpetrators used firearms [1, 15, 22, 32, 33, 34•, 35, 36••, 37,38,39, 42•, 44, 45, 47, 50]. Other studies reported different methods for HS, which were in most cases stabbing, in 4/22 cases (18%) [41, 43, 46, 49] and asphyxia in 2/22 cases (9%) [40, 48].

Focusing on differences between countries, shooting was the main method in the USA (100%); while in other Countries, especially Japan and China [48, 49], other methods were more common (asphyxia and stabbing, respectively). In Europe, the use of firearms was the most common method (63%), but in 27% of studies, different methods were used [40, 41, 43, 46].

Although most studies reported that the same weapon was used to perform both H and S, some did not, for example Flynn (2016; sharp instruments for H and hanging for S) follows: [41], and Verzeletti (2014; the murderer shot or hanged himself after having stabbed or strangulated his wife) [44].

An important factor that might partly explain the different gunshot prevalence as HS method is the deep difference in the worldwide accessibility to guns, related to different gun laws. For example, in the USA, firearms are more commonly legally owned by the population; while in most European countries, the access to guns is restricted [1, 41, 46, 47].

Conclusions

Despite the discrepancies and inconsistencies emerging from the above description, some shared features in the intimate partner HS studies can be identified. Notwithstanding the limited number of studies included in this mini-review, it emerges the need of a shared and common language to describe the motives and reasons for HS, for which relevant classification suggestions have already been proposed.

The association between domestic violence and HS, which is quite consistently reported across different studies, suggests the need to develop prevention strategies targeting this at risk population. The role of substance/alcohol abuse on behalf of perpetrators should be investigated with more detail as a possible trigger of HS events, as it could be a further target for prevention strategies.

Regarding the main methods used for both H and S, suggestions have been raised about firearms regulation being one relevant factor possibly affecting the HS phenomenon [2, 58].