Cycles of solar activity (1960–2023), UV index, serotonin-melatonin, optimism-pessimism, and global GDP with a 1-year lag (1961-2024): R2=0.90

Subject of the study: This paper examines the causal relationship between solar activity cycles (1960-2023) and global GDP growth rates for the period 1960-2024, i.e., with a one-year lag. Methodology: The author develops the methodological approach of W.S. Jevons and A.L. Chizhevsky, supplementing it with the modern biochemical concept of Russell Reiter. Key results: 1. Statistical reliability: A high correlation was found between the indicators: the approximation coefficient was 0.9004. 2. Three-zone biochemical model: The mechanism by which ultraviolet (UV) radiation influences the economy through human neurochemistry is substantiated: - "Biological depression" zone (Wolf number (W) < 20): UV deficiency leads to decreased serotonin levels, causing pessimism and GDP stagnation with a one-year lag. - "Biological optimum" zone (W = 20 - 140): Sufficient serotonin and melatonin levels ensure optimism and peak global GDP growth rates with a one-year lag. - "Biological stress" zone (W > 140): Extreme solar activity suppresses melatonin production (according to R. Reiter's concept), causing "exhaustion pessimism" and a sharp decline in global GDP growth with a one-year lag. 3. The nature of the one-year lag is substantiated. The one-year lag is a consequence of the inertia of economic contracts: the psycho-emotional state of decision-makers in the current year determines the parameters of contracts, the results of which are reflected in the GDP statistics of the following year. 4. Forecast: Based on the model, the expected global GDP growth rates are calculated: 3.1% in 2025 and 3.3% in 2026. A significant slowdown in growth to 1.3% is projected in 2031 due to the solar minimum being reached in 2030.