Depression and Anxiety Emerging From Heavy Metals: What Relationship?

Introduction

Depression is perceived to be a common and serious medical illness among adults. The nature of this disorder has changed considerably in the last twenty years. It is now seen as an acute and self-limiting illness as opposed to a chronic, and lifelong one (J. Johnson, Weissman, & Klerman, 1992). The term depression is depicted as a wide spectrum of symptoms, including depressed mood, sleep disorders, anhedonia, fatigue and loss of energy, lack of concentration, low self-esteem, negative thinking, and suicidality (Cryan, Markou, & Lucki, 2002 ; Wong & Licinio, 2004). Epidemiological studies have shown that depression and anxiety are common throughout the life cycle (Beekman et al., 1998 ; Regier, 1988). Other studies, which were carried out on children, adolescents, and adults have demonstrated the fact that anxiety and depression are closely related(Oliver et al., 2018 ; Werner-Seidler, Perry, Calear, Newby, & Christensen, 2017 ; Yap, Martin, & Jorm, 2018).

Anxiety is defined as a high impact disorder that causes various difficult problems such as excessive worries, motor tension, and fatigue (Nutt, 2005). Some of the different subtypes that anxiety has include general anxiety disorder, panic disorder, social anxiety, agoraphobia, posttraumatic stress disorder, and obsessive-compulsive disorder (Clement & Chapouthier, 1998 ; Nutt, 2005).

Interestingly, patients with depression often have anxiety disorders and those with anxiety disorders have depression as well. Since both disorders may co-occur together, it is very difficult to differentiate between them (Ayis, Ayerbe, Ashworth, & DA Wolfe, 2018 ; Graeff, Guimarães, De Andrade, & Deakin, 1996).Furthermore, epidemiological evidences have revealed that depression is higher in industrialized countries than in non-developed ones (Jaga & Dharmani, 2007). Such a fact may be related to a plausible high exposure to heavy metals in the contaminated areas, which are specifically industrialized zones.

A plethora of studies, indeed, has declared the existence of a relationship between exposure to heavy metals and mood disorders(Berk et al., 2014 ; Dean, Lam, Scarr, & Duce, 2019) where the most important are anxiety and depression (Berk et al., 2014 ; Theorell et al., 2015). To the epidemiological studies, the high level of affection in the industrialized areas was a strong indicator on the link between exposure to heavy metals and mood disorders (Theorell et al., 2015). However, preclinical investigation have presented more than one explanation to the mechanisms underlying the intoxication with heavy metals (Benammi, El Hiba, Romane, & Gamrani, 2014 ; del Blanco & Barco, 2018 ; Yang et al., 2018).

As preclinical and epidemiological studies have advanced knowledge on the effects of intoxication with heavy metals, recent investigation have revealed the existence of a link between the risk of intoxication and the climate change(Ackah et al., 2014 ; del Blanco & Barco, 2018). In fact, the global warming is a strong factor exacerbating the negative effects of heavy metals on human’s health. The actual increase of temperature rise up the amount of released metals in the air as well as in water. Therefore, the amount of intoxicated species become higher, including vegetables, fishes, and many other alimentary products (Ackah et al., 2014 ; Bosch, O’Neill, Sigge, Kerwath, & Hoffman, 2016 ; Kohzadi, Shahmoradi, Ghaderi, Loqmani, & Maleki, 2018). As a result, the ways of human being’s infection turn out to be more important. Between this and that, the risk of infection remain a real threat not only to the ecosystem and human’s wellbeing, but also for the future generations.