Other causes include:

Immunological diseases
Extreme climatic conditions
Prolonged deficiency to iron and vitamins in the diet

Pathogenesis
"Exposure to areca nut (Areca catechu) containing products with or without tobacco (ANCP/T) is currently believed to lead to OSF in individuals with genetic immunologic or nutritional predisposition to the disease. "This hypersensitivity reaction results in a juxta-epithelial inflammation that leads to increased fibroblastic activity and decreased breakdown of fibers. The fibroblasts are phenotypically modified, and the fibers they form are more stable, produce thicker bundles that progressively become less elastic. once the original loosely arranged fibrous tissue is replaced by the ongoing fibrosis, the movability of the oral tissues is reduced, there is loss of flexibility and reduced opening of the mouth. These collagen fibers are non degradable and the phagocytic activity is minimized. According to a  recent cross sectional study the time taken for return  of salivary pH to baseline levels after chewing areca nut containing mixtures is significantly longer in habitual users with  OSF when compared to unaffected users. Prolonged Alkaline pH induces death fetal fibroblast type and replacement by a profibrotic fibroblast. The patterns of intraoral fibrotic bands produced by alkaline chemical injury mimic those produced by areca nut chewing. Sharma et al., have equated the pathogenesis of OSF to an over-healing  wound, to explain its evolution as well as malignant transformation. Increased mechanical stiffness through YAP/TAZ pathway accelerates the malignant transformation of OSF.
Oral submucous fibrosis is a chronic, complex, premalignant (1% transformation risk) condition of the oral cavity, characterized by juxta-epithelial inflammatory reaction and progressive fibrosis of the submucosal tissues (the lamina propria and deeper connective tissues). As the disease progresses, the oral mucosa becomes fibrotic to the point that the person is unable to open the mouth. The condition is remotely linked to oral cancers and is associated with areca nut and / or its by-products chewing, majorly practiced in South and South-East Asian countries. The incidence of OSMF has also increased in the western countries due to the changing habits and constant migrating population. Definitions
Per Jens J Pindborg and Satyavati Sirsat (1966) (Pathological definition)-
An insidious chronic disease affecting any part of the oral cavity and sometimes the pharynx. Although occasionally preceded by and/or associated with vesicle formation, it is always associated with a juxta-epithelial inflammatory reaction followed by a fibro-elastic change of the lamina propria, with epithelial atrophy leading to stiffness.Per Mohit Sharma and Raghu Radhakrishnan (2019) - An insidious, chronic potentially malignant fibrotic disorder affecting the entire oral cavity and sometimes the pharynx and oesophagus.