**5. Conclusions**

Problems related to nutrition are often overlooked in patients with common mental health disorders (such as depression, anxiety, ADHD and ASD) towards interventions focused on medication complemented by behavior/psychotherapy treatments. Current research within the nutritional psychiatry area provides evidence regarding the role of nutrition and diet on these psychiatric conditions and offers a basis for developing new evidence-based intervention plans from a multidisciplinary perspective. Given the multifaceted and complex nature of mental and neurodevelopmental problems, the onset at early ages of the child (particularly for ADHD and ASD) and its persistent presentation across development stages (from early childhood to older age), the findings of these works could also contribute to the elaboration of guidelines/recommendations for improving the caring capacity of healthcare practitioners and family caregivers. In the end, improving the nutritional status of the patient will contribute to the individuals' wellbeing and facilitate better progression of medical conditions.

However, the design of effective dietary plans is based on the existence of reliable and valid assessment tools. Unfortunately, the current evidence does not propose nutritional assessment instruments specifically developed for individuals with different mental disorders (such as depression, anxiety, ADHD and ASD). Nutritional psychiatric research warrants additional attention and effort, combining varied methodologies and analyzing larger groups (clinical and population-based samples). Therefore, based on the existing research, dietary markers (foods variety, nutrients intake, sensory issues, preferences/restrictions and dietary intakes), biochemical indexes (vitamins, proteins, minerals, carbohydrates, lipids and other essential nutrients) and anthropometric evaluation (length-for-age, weight-forage, weight-for-length, head circumference and other age-related-developmental indexes) should be key components of these measurement tools.

As a final thought, the study of how nutrition and mental health are linked is a growing research area, and the results obtained so far are highly promising. The ultimate objective is to facilitate new strategies for improving the quality of life and health of people with mental illness and to prevent the onset, aggravation and negative impacts of diseases.

**Funding:** This research received no external funding.

**Data Availability Statement:** No original data has been analyzed for this manuscript.

**Acknowledgments:** This manuscript was supported by the Catalan Institution for Research and Advanced Studies (ICREA-Academia, 2021-Programme). This funding institution had no role in the writing of the manuscript, or the decision to submit the paper for publication.

**Conflicts of Interest:** The authors declare no conflict of interest.
