Mental Health Self-Check (PHQ-9 Style)
Answer 9 questions about your mood, sleep, and energy over the past two weeks.
Get a score with general guidance.
This is not a diagnostic tool.
BMI (Body Mass Index) is a screening tool that uses height and weight to classify body composition into standard categories. While originally designed as a population-level metric, research has also examined its relationship with psychological well-being, self-esteem, and mental health outcomes.
BMI formula:
BMI = Weight (kg) / Height (m)²
BMI (Imperial) = (Weight (lbs) × 703) / Height (inches)²
Standard BMI categories (WHO):
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity Class I |
| 35.0 – 39.9 | Obesity Class II |
| 40.0+ | Obesity Class III (Severe) |
Worked example: A person 175 cm (1.75 m) tall, weighing 82 kg:
- BMI = 82 / (1.75)² = 82 / 3.0625 = 26.8 → Overweight
BMI and mental health — research findings:
- Both underweight (BMI < 18.5) and severe obesity (BMI ≥ 35) are associated with higher rates of depression and anxiety in large population studies
- The relationship is bidirectional: mental health conditions can cause weight changes, and weight changes affect mental health
- Body image dissatisfaction — regardless of actual BMI — is a stronger predictor of depression than BMI itself
- Social stigma around weight affects mental well-being independently of physical health
Critical limitations of BMI:
- Does not measure body fat percentage directly
- Does not account for muscle mass (athletes often score “overweight”)
- Does not reflect fat distribution (visceral vs. subcutaneous fat)
- Less accurate for elderly populations, children, and some ethnic groups
Better complementary measures: Waist-to-height ratio (WHtR < 0.5 is healthy), waist circumference, and DEXA body composition scans provide a more complete picture.