However, scientists regard the overall data as insufficient due to the "difficulties of undertaking such studies.
haʊˈɛvɚ, sˈaɪəntɪsts ɹᵻɡˈɑːɹd ðɪ ˌoʊvɚɹˈɔːl dˈeɪɾə æz ɪnsəfˈɪʃənt dˈuː tə ðə "dˈɪfɪkˌʌltiz ʌv ˌʌndɚtˈeɪkɪŋ sˈʌtʃ stˈʌdiz.