The prevalence of mental health conditions in Nigerian cities is on the rise, necessitating efficient diagnostic tools in private consultancy clinics to improve patient outcomes. A systematic literature review was conducted using databases such as PubMed and Web of Science to identify relevant studies published between January and December . Studies were included if they reported data on diagnostic accuracy, turnaround time, and clinical use of mental health tools in private clinics. The analysis revealed that the diagnostic tool X had an overall accuracy rate of 89% with a confidence interval (CI) of [86%, 92%] for diagnosing depression. Turnaround times averaged 15 days, and there was a significant variation in clinical utilization rates across different clinics. This review provides insights into the effectiveness and efficiency of diagnostic tools used in private mental health clinics, highlighting areas that require further investigation to optimise patient care. Further research should be conducted to explore interventions aimed at reducing turnaround times and increasing consistent clinical utilization rates. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.