Several limitations should be noted. Major limitations are the incomplete sample participation in young adulthood, possible unmeasured underlying susceptibility factors, (e. G., familial influences), and some researchers might question the reliability of the TD instrument for measuring drug dependence.

The researchers must note key limitations for measuring dependency on drugs. The inadequate representative participation in young adulthood; unmeasured ultimate susceptibility factors like familial influences; may interrogate the credibility of the instrument TD.

Explanation:

As per the question, the given paragraph regarding the TD instrument can be revised as mentioned above in order to give it a more precise and coherent form. The author lays emphasis on noting down the major constraints for estimating the reliance over the drugs which include the insufficient sample participation that causes the fundamental sensitivity factors to be ignored. This ignorance directly poses threat to the credibility of the instrument by questioning its validity. Thus, they need to jotted down adequately to ensure efficacy of the research.