**3. Conclusions**

This paper summarizes the recent literature on the potential role of exerciseinduced neurotrophic factors on mental health. This paper indicates that there is much evidence that the enhancement of neurogenesis, angiogenesis, and synaptogenesis caused by exercise-induced neurotrophins and growth factors, such as the BDNF, IGF-1, irisin, and VEGF, etc., has an essential role in the positive changes of mental health including depression, anxiety, cognition and psychosis. Nevertheless, there is currently insufficient evidence to draw firm conclusions regarding the relationship between optimum exercise regimes to maximize mental health via modulation of neurotrophic factors.

#### *The Potential Role of Exercise-Induced Neurotrophic Factors for Mental Health DOI: http://dx.doi.org/10.5772/intechopen.106867*

It is also important to note that there is a considerable gap in evidence [126] for the causative relationship between exercise, neurotrophic factors, and brain function and exercise's effect on neuropsychiatric function. Moreover, compared to BDNF, the most studied neurotrophic factor, there is still insufficient evidence for a clear explanation of the association between exercise and other candidates such as irisin, IGF-1, and VEGF levels or their-mediated exercise benefit on mental disorders. A mental disorder may have many symptoms affecting multiple neural processes [127]. The contradictory results from studies due to the wide variety of symptoms make it challenging to target a disorder itself- or symptoms-specific exercise prescription to optimize mental health.

On the other hand, although numerous previous studies reported the beneficial effect of exercise on mental health, it should consider that the effect level highly depends on the type, duration, frequency and intensity of the exercise regime. Exercise variables that provide different cognitive, metabolic, or physiological loads can cause different neurotrophic factors to be released [128]; therefore, the effects of different types of exercises on the neurochemical system and mental disorders may also be unique to them. Understanding the crosstalk between dynamic neurobiological factors and exercise variables (type, frequency, intensity, etc.,) may help optimize personalized mental health exercise programs.

While the studies examining the beneficial effects of exercise on mental health have focused on long-term adaptations, the acute beneficial effects of exercise mediated by peripheral neurotrophic factors are not well characterized. It must be taken into consideration that investigating acute responses to an exercise might help us to explain the underlying functional and molecular mechanisms of how long-term mental health adaptation occur. Due to the positive neurotrophic factor responses from different types of exercise, studies can be planned to evaluate whether multimodal exercise interventions which combine AE, RE or cognitive exercise methods can contribute a greater beneficial effect on mental health.

The social distancing and/or isolation period during the COVID-19 pandemic led greater prevalence of mental health disorders such as depression and anxiety [129]. Considering that the pandemic is not over yet and isolation obligations are possible in other diseases in the future, the planning of exercise programs such as exergame that people can apply at home will be important in maintaining mental health [130].

Lastly, considering that there is still no fully invasive or pharmacologically effective treatment for mental health, it makes sense to exploit the potential of exercise to produce beneficial effects on mental health through neurotrophic factors. Besides the fact that exercise can improve mental health, it can also provide other benefits such as improved quality of life, good sleep quality, increased muscle mass, and greater cardiovascular condition. These benefits will be far more inclusive than the current pharmacological treatments.

### **Acknowledgements**

I would like to thank all the precious scientists in the references section for their valuable contributions to the field.
