How do Tibeto-Burman languages distinguish causative verbs from noncausative verbs?

In many Tibeto-Burman languages, the distinction between causative and noncausative verbs is achieved through morphological processes rather than inflectional categories like voice.1

These languages typically signal the causative relationship using one of the following methods:

• Prefixes: Some languages use different prefixes to mark the distinction. For example, in Written Tibetan, mnam means "have a smell," while the causative form snam means "smell something".1
• Consonant or Tone Alterations: Other languages utilize secondary changes in the initial consonant or the tone of the verb. In Written Burmese, for instance, the intransitive nôi ("awaken") is distinguished from the transitive causative hnôi ("wake someone"). Similarly, in Lahu, the verb vâʔ ("hide oneself") contrasts with the causative fá ("hide something").1
• Semantic Bleaching: Additionally, some isolating languages express causative relationships by using full verbs—such as those meaning "give," "put," or "finish"—that have undergone semantic bleaching to function as grammatical markers for causative categories.1