The World Health Organization (WHO) defines violence as: "The intentional use of physical force or power, threatened or actual, against oneself, another person or against a group or community, which either results in or has a high likelihood of resulting in, injury, death, psychological harm, maldevelopment or deprivation." ¹

Based on this definition WHO splits violence into three broad categories, i.e., self-directed violence; interpersonal violence; and collective violence. Self-directed violence includes suicidal behavior (i.e., suicidal ideation, plans, attempted suicide, and suicide). Interpersonal violence by itself divides into two categories, i.e., family and intimate partner violence (e.g., child abuse, violence by an intimate partner and abuse of the elderly) and community violence (e.g., youth violence, rape or sexual assault by strangers and violence in institutional settings). Collective violence includes wars and armed conflicts within or between states, genocide, and terrorism. ²

Collective violence as like as other types of violence is related to human distress and is disastrous, which is dealt with elsewhere. ³ , ⁴ , ⁵ , ⁶ , ⁷ Nonetheless, the results of a few recent studies ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ , ¹⁵ , ¹⁶ suggest that both self-directed violence and interpersonal violence might increase after natural disasters, e.g., earthquake, flood, tropical cyclones etc.

In the present article therefore, I am going to focus on the relation between violence and natural disasters by looking at the literature, and recommend more well-planned epidemiological studies. I begin with the underlying associations between natural disasters and violence.

Natural disasters might increase the rate of violence both in the short and long-term, in a number of ways. ¹⁶ For instance, in the aftermath of a natural disaster mental distress among the affected population will increase. There is evidence, which suggests that between a third and half of all persons exposed to natural disasters will finally develop mental distress, e.g., post-traumatic stress disorder (PTSD), depression, anxiety disorders, etc. ¹¹

Personal threats to life, loss of loved ones, property loss, immense destruction, breakdown of social security systems, collapse of social cohesion and harmony and so on, are the most important reasons behind this trend and diverse studies highlight that the effects of catastrophic disasters on mental health are larger than mild ones. ⁸ , ⁹ , ¹⁰ , ¹² , ¹³ , ¹⁴ , ^15.

Furthermore, due to the scarcity of basic provisions, failure of law enforcement, powerlessness, aggravation caused by a fraudulent bureaucracy and forgotten governments′ promises to help victims, etc. it would be possible that the semental distresses will develop into violence, either self-directed ¹³ or interpersonal. ¹⁶

In the path of relation between being exposed to natural disaster and developing mental distress, which leads to one form of violence, there are also a number of other variables. ¹⁷ For example, it has been shown that women, children, elderly, low-income and those people who have been exposed to a previous traumatic event are more vulnerable to developing mental distress ¹⁸ , ¹⁹ or being a victim of violence in the aftermath of natural disasters. ¹⁶

It is also vital to realize that being exposed to one natural disaster might amplify the adverse psychological outcomes of being exposed to subsequent natural disasters. ²⁰ Furthermore, those people who received social ¹⁹ or religious ²¹ , ²² support were less vulnerable to developing such adverse psychological outcomes.

All the above discussions are depicted in Figure 1. The key point in this figure is that how the anger and the stress of those who exposed to natural disasters are expressed inwardly, i.e., self-directed or outwardly, i.e., interpersonal violence. Figure 1

The underlying associations between natural disasters and violence

I searched the literature using a well-known search engine, i.e., PubMed (http://www.ncbi.nlm.nih.gov) from 1/1/1978 to 31/12/2011. Thirteen keywords were selected which included "flood," "hurricane," "drought," "cyclone," "tornado," "volcanic eruption," "earthquake," "blizzard," "tsunami," "avalanche," "famine," "natural disaster," and "violence."

A search strategy was built applying advanced search capability of the search engine. Based on this search strategy, only those articles were retrieved that had one of the first 12 keywords plus the 13 keyword either in the title or the abstract. This strategy retrieved 70 articles.

The inclusion criteria as set out that only original article that explicitly dealt with violence after natural disasters and written in English was included. From 70 numbers of retrieved papers only a handful was original and explicitly dealt with violence after natural disasters.

Therefore, in the next step, I also looked at the reference list of the retrieved papers and searched other search engines such as Scopus. Having carried out that, there was still a shortage of original research regarding these important topics and I have totally retrieved only 21 articles that met the inclusion criteria Table 1. Nevertheless, below are the results of these search strategies, which were summarized for self-directed and interpersonal violence, separately.{Table 1}

Mental disorders are among the strongest risk factors for self-directed violence, i.e., suicidal behavior ²³ , ²⁴ and as it has been mentioned earlier, being exposed to natural disasters will increase the likelihood of developing mental disorders. ¹¹ Therefore, a relation between being exposed to natural disasters and developing suicidal behavior would also be possible. ²⁵

The literature review highlights that there are only a few studies, which focus on this relationship and report that being exposed to a natural disaster such as hurricane, cyclone and earthquake, might increase the rates of suicide ²⁶ , ²⁷ , ²⁸ , ²⁹ , ³⁰ , ³¹ , ³² or suicidality. ³³ , ³⁴ , ³⁵ , ³⁶ , ³⁷ One of these studies ²⁷ later retracted some of its initial findings due to errors in its analyses. ³⁸

The results of one study ³⁵ have revealed that suicidal behavior might manifest years after a natural disaster, i.e., earthquake has occurred. This seems to be related to "the quarrels among families regarding sharing the financial burden of rebuilding the house, the poor control of mental disease owing to the disorganized health-care systems, the lack of social and financial support during the harsh rebuilding process, the powerlessness, and the frustrations caused by a corrupt bureaucracy," ¹³ and not the shock of the disaster per se.

The literature review also highlight that there are only a few studies, which focus on the relation between being exposed to a natural disaster and the rates of interpersonal violence. ¹⁶ The results of these studies reveal that being exposed to natural disasters such as tsunami, hurricane, earthquake, and flood increases the violence against women and girls, e.g., rape and sexual abuse, ³⁹ , ⁴⁰ , ⁴¹ intimate partner violence, ³² , ⁴² , ⁴³ , ⁴⁴ child PTSD, ⁴⁵ child abuse, ⁴⁶ , ⁴⁷ and inflicted traumatic brain injury. ⁴⁸

However, it should be noted that there is also one published study, which reported no significant variations in any of the measures of sexual violence toward women in the periods before and after a natural disaster, i.e., hurricane. ⁴⁹

Since in the aftermath of natural disasters women and children may be separated from their family, they are often at greater risk of being subject to interpersonal violence. ¹⁶ Therefore, in such situations proper attention should be paid to the needs of these vulnerable groups.

These include: Swift identification of separated children and reunification of them with their official guardians, ⁵⁰ providing secure places for single women and girls ³⁹ and providing proper health services, counseling, and legal support for the victims of such violence. ¹⁶ , ⁵¹

The relation between being exposed to natural disaster and being a victim of violence either self-directed or interpersonal is coming to light with recent studies. Natural disasters might increase the rate of violence both in the short and long-term by developing mental distress and anger. The key point is that how the exposed population reacts to these pressures either inwardly or outwardly.

Although, there is a scarcity of research in this area the potential threats of violence after natural disaster should not be neglected by the scientific community. Therefore, given the alarming increase of natural disasters during recent decades ⁵² , ⁵³ , ⁵⁴ it is time to design and conduct more methodological sound studies. ⁵⁵ The chief aims of these studies are to understand how natural disasters form and/or change the pattern of violence within the community and to recommend the most useful structure of support services.

The following approaches could be recommended for further epidemiological research in this area:

The length of the study should be long enough to allow scientists to determine any possible relation between being exposed to natural disasters and being a victim of violence. However, it should be noted that although long-term follow-up is important it does not mean that one should overlooked the importance of getting in the field as fast as possible.