A statistical theory is developed in order to describe the pressure-induced shift and broadening of spectral holes in pressure-tuning experiments in crystals. The theory accounts for the defect-related diaelastic effect (induction of internal inhomogeneous strain fields by the applied hydrostatic pressure due to the host-defect compressibility and/or size mismatch). General results are specified and analyzed in the case of similar defects and for two different types of point defects. The former case yields no hole broadening, while the latter one does. A similar consideration applies to electric-and magnetic-field-induced effects on spectral holes in crystals as well.